I'd first try using the app "
Large Address Aware", to make the game use more memory than what its maximum set amount was when it left the publisher in 2007, which was no more than 2 gigs of memory. You may have more memory than that (you say you've got 4 gigs), but the game won't use any more than 2 gigs unless you force it to.
Second, take the mods out of JSGME "Activation", then run the "Compare Snapshot" feature to compare your original game files (when you first installed the game and JSGME), with what you have now. Comparing stock game files is the only way of knowing whether you still have a good game install or a corrupted one from using mods. Didn't take a "Snapshot" as the instructions in JSGME state? Start over with a good removal of the game, then a clean re install.