Well Jimbuna, ya put him in the ATO, Atlantic Theatre of Operations(of course), which insinuates that underwater2 has SH4 v1.5, Uboats Missions (or Gold), not v1.4...
underwater2, you can only use mods that are v1.4 compatible, which are few and far between anymore. There is an "original" version of Fall of the Rising Sun (~NOT~ the newer Ultimate), and some of Webster's mods, but be sure and read the ReadMe files to be certain of compatibility. De-activate all your mods in JSGME, and try again. It might be though, if you didn't take a "Snapshot" in JSGME with which to "Compare Files" with, that you might have to un-install SH4 completely, then re-install it (and update to v1.4 again).
If you've got a SH4 DVD disk, and have it "patched" to v1.4, you can keep that, and then make a parallel install of it (copy and rename the SH4 WotP folder), and then do a
Uboat Missions Add-On download from Amazon or similar, or just do the whole package
Silent Hunter 4 Gold Edition. Either way works, and you get more mods. One thing you cannot do is use the Steam Uboats Missions with a disk version of v1.4 or 1.3, and vice versa... btw, using those links should give the site here a "commission", but doesn't raise your price at the store.