Here are some things you can try, if you haven't already. First, make sure the directory for the game is set in the Modman application. Be sure that the application for the game is selected when you are checking the directories.
Second, make sure you are launching the game modded, instead of launching it vanilla from the Modman application. I see some people make the mistake of not launching the game modded, so I always gotta consider that and put the suggestion out there.
Third, try launching the game with one mod loaded at a time (unless there are dependencies.) Sometimes, there can be conflicts, if the mod isn't up-to-date.
If any of these don't work, try letting me know what else you have tried.
