You probably know this already but basically the current IGT is incompatible with the newest TiC 1.8.
This includes that the new weapons do not respect IGT features so does the creative menu crash since I updated TiC, not sure if it is IGT though. Crashlog

Several members on our servers have also had this crash doing the exact same action (trying to search for items in the creative menu) as well as another more specific crash pointing to IGT http://pastebin.com/Nr2hBr0V