Rename libPortability.dll to libPortability.dll.orig, and copy libPortabilityNOSH.dll to libPortability.dll.
Do this in:
C:\Xilinx\14.5\ISE_DS\common\lib\nt64 (copy dll from first location)
This turns off SmartHeap.
This will fix ISE and iMPACT crashes on file dialogs.
This information was found from another thread, thank you howardp from Xilinx in this thread:
Please note: this doesn’t resolve Vivado or PlanAhead issues. This only helps for ISE and iMPACT on Windows 8 x64.
Thanks again to Hamster for the tip!
(via the forums)