Update: We have temporarily disabled LFG listings until we can get a proper fix in for this.
We are aware of a crash that can occur when entering WvW. This is an issue with the LFG preview UI in the party UI:
There is a work around that can midigate some of the issue though it is not a proper fix but can help get people back into WvW sooner than we can have a patch ready. Unchecking the "Automatically Expand LFG Preview" will allow you to enter WvW without crashing. The LFG preview UI can still cause a crash so be careful using it while in WvW.