I recently installed FOOK and had it enabled for a couple days, but I disabled it when I noticed that it was causing a few glitches. Now my character is suffering a -10 penalty on both Barter and Speech for no apparent reason. Could something in FOOK have caused this? I
really need my Speech skill...
If you still have a savegame available that used FOOK (check using the 'Save game list' button in FOMM): Try re-enabling FOOK, loading that save, un-equip any apparel or other items that have any bonus effects, and make a new savegame. Quit, disable FOOK, load this new savegame and check your stats.
If the previous method doesn't work, you can 'cheat' with some console commands to try to get the final skill back to what it should be. First type "player.getavinfo barter" to see if there is already a "SetAV Override" value (if it's not there, it's zero). Then type "player.setav barter X", where X is that value +/- how much you want to change - so if the "SetAV Override" value was 4, you'd type "player.setav barter 14" to counteract your -10 Barter penalty. Do the same steps for Speech.
This won't remove the -10 displayed on your Stats>EFF screen, but will balance it out. I don't know if there is a way to change the Temp modifiers from the console - would be nice if there was.
NOTE: using setav on SPECIAL attributes overrides the actual base value, rather than adding/subtracting to it.