Ok, so my textures work perfectly when I test it through Eclipse.  However, when I build the jar and then subsequently test it, the textures for some blocks and items just didn't work.  The code referenced the textures correctly, yet the textures didn't work.  I'll check through the console to see if there's any errors or missing references.

Yeah, just figured that out.  D'oh!  *facepalm*  I sent a message to my modmaking partner, Syxes.  Might want to help him with coding, as he's just getting into the nitty gritty of forge modding.