Please
enable logging and upload your Lua.log and Database.log - without these, hunting down the exact source of the problem is a guessing game.
looks like its logging this:
[284026.062] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284026.218] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284029.515] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284033.656] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284041.140] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284041.156] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284042.156] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284043.687] TechTree: popupInfo.Data1: 0
[284043.687] TechTree: popupInfo.Data2: -1
[284043.703] TechTree: popupInfo.Data3: 0
[284043.703] Runtime Error: C:\Users\Sean\Documents\My Games\Sid Meier's Civilization 5\MODS\JFD's and Pouakai's Mercenaries (v 6)\Lua\UI\Overrides\JFD_TechButtonInclude.lua:397: attempt to call field 'Tech_SpecialistYieldChanges' (a nil value)
[284054.875] InstalledPanel: Refreshing Mods
[284054.875] InstalledPanel: GetModBrowserListings()
[284054.906] InstalledPanel: Refreshing Mods
[284054.906] InstalledPanel: GetModBrowserListings()