The Java Console just gets spammed with:
2012-11-06 16:35:35 [iNFO] [sTDOUT] ########## GL ERROR ##########
2012-11-06 16:35:35 [iNFO] [sTDOUT] @ Pre render
2012-11-06 16:35:35 [iNFO] [sTDOUT] 1281: Invalid value
IF I cause a crash upon logging in, by installing the incompatible WorldEditCUI for exmaple, the crash report sometimes logs all of the floating items on the showcases.
Screenshots:
http://t3chguy.imgur.com/all/
The first one is with Forge OFF, second ON. You can see the difference, there is no actual crash, just no visible items in the shop.