So......you've got a stock SH4 patched to 1.5!? Ok, that's a good start. You're running Windows 8 and have the "Main" game folder (Silent Hunter Wolves of the Pacific) placed somewhere other than the "Programs" folder. That's good, every OS newer than Windows XP should NOT have the game placed in the "Programs" folder (has to do with running the game as administrator and the "permissions" bunch of crap).
Have you deleted the folder named "SH4" found in the "Documents" folder of your computer (it could be under some other named folder like "Documents and Settings".....this folder has been renamed by almost every different OS since XP). The "SH4" folder is created every time the game is started for the first time. It holds your option settings for the game, and any saved game points made while playing. It's always good to delete this folder's contents if things seem to run screwy. You'll lose any saved games, and your resolution settings will need to be reset, but that's a small price to pay to have the game run correctly. Just for the sake of keeping things running smothly I'll delete the SH4 folder contents anytime I make a large change with mods through JSGME.
I wasn't able to tell from your replies, this problem occurs
without running any mods? Just the stock game? If so, I'm guessing a reinstall is in order of the game. Follow the instructions for a clean install found in
this sticky thread. And for sure, take a "snapshot" of your clean game files just after adding JSGME. You'll use this snapshot of your game files to compare a future image of your game files if things turn sour again (and they will if you mod your game).