http://forums.2kgames.com/showthread.php?215716-If-you-re-having-troubles-launching-WorldBuilder
This works like a treat.
1) Open the Civilization V SDK entry from within Steam. This will display the Launcher which allows you to choose between ModBuddy, WorldBuilder, the Tuner etc.
2) Right click anywhere on the launcher and select "Create Desktop Shortcut to WorldBuilder". This will create a shortcut on your desktop that goes directly to WorldBuilder.
*Here's where the work around starts*
3) Locate the WorldBuilder desktop shortcut and right click on it, then select Properties.
4) Select the "Shortcut Tab".
5) Where it says Target:, Add just after the last " -PromptForGamePath.
Your target should look something like this:
"C:\Program Files (x86)\Steam\steamapps\common\Sid Meier's Civilization V SDK\WorldBuilder\x86\WorldBuilder.exe" -PromptForGamePath
*NOTE that -PromptForGamePath happens AFTER the quotation mark.
6) Launch the Shortcut. This will bring up a new dialog asking if you'd like to manually select a Civ5 exe. Say Yes.
7) Navigate to where your Civ5 exe is stored.
For me, it was C:\Program Files (x86)\Steam\steamapps\common\Sid Meier's Civilization V\CivilizationV.exe
Hit OK!
8) You will notice the Civ5 Launcher comes up.. Select the DX9 version of Civ.
9) Everything should be good to go!