It seems to be that it can't find the paper code under Item.class when my mod calls for it. The funny thing is, this is only in the actual game, whereas MCP's startclient.bat version is just fine. My code is as follows:
I have a few other mods, including TMI, Single Player Commands, zeppelin, airship, another mod I made for practice that adds the "Ghast Blaster" (a wand that launches Ghast fireballs), Modloader, the HD patcher, and possible others. These mods worked perfectly together before the addition of my gun mod.
If anyone has some advice, please tell me.