What's causing my game to freeze?

I tried to create a mod which gives me an "enormous" map size. The map size was designed to be about five times bigger than the "huge" map size, both vertically and horizontally, effectively resulting in 25 times the overall map size. It was designed to take the maximum 18 civs, by default (as opposed to Huge's 11) and give plenty of room to spread my empire before cultural borders start sparking tensions.

However, whenever I try to start a game with this map, it always freezes.

I'm attaching the XML file. Have I programmed it wrong, or do I just need more ram (I have 4GB)?

EDIT: Ok, I tried to upload the XML file, but for whatever reason, this site says it's an invalid file. Don't know why that is. So, I'll just copy-and-paste the contents of the XML file in a spoiler section:

Spoiler :

<?xml version="1.0"?>
<!-- edited with XMLSPY v2004 rel. 2 U (http://www.xmlspy.com) by Jesse Smith (Firaxis Games) -->
<!-- Sid Meier's Civilization 4 -->
<!-- Copyright Firaxis Games 2005 -->
<!-- -->
<!-- World Infos -->
<Civ4WorldInfo xmlns="x-schema:CIV4GameInfoSchema.xml">
<WorldInfos>
<WorldInfo>
<Type>WORLDSIZE_DUEL</Type>
<Description>TXT_KEY_WORLD_DUEL</Description>
<Help>TXT_KEY_WORLD_DUEL_HELP</Help>
<iDefaultPlayers>2</iDefaultPlayers>
<iUnitNameModifier>50</iUnitNameModifier>
<iTargetNumCities>4</iTargetNumCities>
<iNumFreeBuildingBonuses>1</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>0</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>-50</iMaxConscriptModifier>
<iWarWearinessModifier>50</iWarWearinessModifier>
<iGridWidth>10</iGridWidth>
<iGridHeight>6</iGridHeight>
<iTerrainGrainChange>-1</iTerrainGrainChange>
<iFeatureGrainChange>-1</iFeatureGrainChange>
<iResearchPercent>100</iResearchPercent>
<iTradeProfitPercent>80</iTradeProfitPercent>
<iDistanceMaintenancePercent>50</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>45</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>11</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_TINY</Type>
<Description>TXT_KEY_WORLD_TINY</Description>
<Help>TXT_KEY_WORLD_TINY_HELP</Help>
<iDefaultPlayers>3</iDefaultPlayers>
<iUnitNameModifier>40</iUnitNameModifier>
<iTargetNumCities>4</iTargetNumCities>
<iNumFreeBuildingBonuses>1</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>0</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>-25</iMaxConscriptModifier>
<iWarWearinessModifier>30</iWarWearinessModifier>
<iGridWidth>13</iGridWidth>
<iGridHeight>8</iGridHeight>
<iTerrainGrainChange>-1</iTerrainGrainChange>
<iFeatureGrainChange>-1</iFeatureGrainChange>
<iResearchPercent>110</iResearchPercent>
<iTradeProfitPercent>70</iTradeProfitPercent>
<iDistanceMaintenancePercent>60</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>40</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>10</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_SMALL</Type>
<Description>TXT_KEY_WORLD_SMALL</Description>
<Help>TXT_KEY_WORLD_SMALL_HELP</Help>
<iDefaultPlayers>5</iDefaultPlayers>
<iUnitNameModifier>30</iUnitNameModifier>
<iTargetNumCities>5</iTargetNumCities>
<iNumFreeBuildingBonuses>3</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>25</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>0</iMaxConscriptModifier>
<iWarWearinessModifier>10</iWarWearinessModifier>
<iGridWidth>16</iGridWidth>
<iGridHeight>10</iGridHeight>
<iTerrainGrainChange>0</iTerrainGrainChange>
<iFeatureGrainChange>0</iFeatureGrainChange>
<iResearchPercent>120</iResearchPercent>
<iTradeProfitPercent>60</iTradeProfitPercent>
<iDistanceMaintenancePercent>70</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>35</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>9</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_STANDARD</Type>
<Description>TXT_KEY_WORLD_STANDARD</Description>
<Help>TXT_KEY_WORLD_STANDARD_HELP</Help>
<iDefaultPlayers>7</iDefaultPlayers>
<iUnitNameModifier>20</iUnitNameModifier>
<iTargetNumCities>5</iTargetNumCities>
<iNumFreeBuildingBonuses>5</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>50</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>25</iMaxConscriptModifier>
<iWarWearinessModifier>-10</iWarWearinessModifier>
<iGridWidth>21</iGridWidth>
<iGridHeight>13</iGridHeight>
<iTerrainGrainChange>0</iTerrainGrainChange>
<iFeatureGrainChange>0</iFeatureGrainChange>
<iResearchPercent>130</iResearchPercent>
<iTradeProfitPercent>50</iTradeProfitPercent>
<iDistanceMaintenancePercent>80</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>30</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>8</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_LARGE</Type>
<Description>TXT_KEY_WORLD_LARGE</Description>
<Help>TXT_KEY_WORLD_LARGE_HELP</Help>
<iDefaultPlayers>9</iDefaultPlayers>
<iUnitNameModifier>10</iUnitNameModifier>
<iTargetNumCities>6</iTargetNumCities>
<iNumFreeBuildingBonuses>6</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>75</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>50</iMaxConscriptModifier>
<iWarWearinessModifier>-30</iWarWearinessModifier>
<iGridWidth>26</iGridWidth>
<iGridHeight>16</iGridHeight>
<iTerrainGrainChange>1</iTerrainGrainChange>
<iFeatureGrainChange>1</iFeatureGrainChange>
<iResearchPercent>140</iResearchPercent>
<iTradeProfitPercent>40</iTradeProfitPercent>
<iDistanceMaintenancePercent>90</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>25</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>7</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_HUGE</Type>
<Description>TXT_KEY_WORLD_HUGE</Description>
<Help>TXT_KEY_WORLD_HUGE_HELP</Help>
<iDefaultPlayers>11</iDefaultPlayers>
<iUnitNameModifier>0</iUnitNameModifier>
<iTargetNumCities>6</iTargetNumCities>
<iNumFreeBuildingBonuses>7</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>100</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>75</iMaxConscriptModifier>
<iWarWearinessModifier>-50</iWarWearinessModifier>
<iGridWidth>32</iGridWidth>
<iGridHeight>20</iGridHeight>
<iTerrainGrainChange>1</iTerrainGrainChange>
<iFeatureGrainChange>1</iFeatureGrainChange>
<iResearchPercent>150</iResearchPercent>
<iTradeProfitPercent>30</iTradeProfitPercent>
<iDistanceMaintenancePercent>100</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>20</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>6</iNumCitiesAnarchyPercent>
</WorldInfo>
<WorldInfo>
<Type>WORLDSIZE_ENORMOUS</Type>
<Description>TXT_KEY_WORLD_HUGE</Description>
<Help>TXT_KEY_WORLD_HUGE_HELP</Help>
<iDefaultPlayers>18</iDefaultPlayers>
<iUnitNameModifier>0</iUnitNameModifier>
<iTargetNumCities>8</iTargetNumCities>
<iNumFreeBuildingBonuses>8</iNumFreeBuildingBonuses>
<iBuildingClassPrereqModifier>100</iBuildingClassPrereqModifier>
<iMaxConscriptModifier>75</iMaxConscriptModifier>
<iWarWearinessModifier>-50</iWarWearinessModifier>
<iGridWidth>160</iGridWidth>
<iGridHeight>100</iGridHeight>
<iTerrainGrainChange>1</iTerrainGrainChange>
<iFeatureGrainChange>1</iFeatureGrainChange>
<iResearchPercent>200</iResearchPercent>
<iTradeProfitPercent>35</iTradeProfitPercent>
<iDistanceMaintenancePercent>110</iDistanceMaintenancePercent>
<iNumCitiesMaintenancePercent>15</iNumCitiesMaintenancePercent>
<iNumCitiesAnarchyPercent>6</iNumCitiesAnarchyPercent>
</WorldInfo>
</WorldInfos>
</Civ4WorldInfo>