Two suggestions:
First, install the 4GB Patch.
http://www.subsim.com/radioroom/down...o=file&id=2888. You are running Win8 and have 8 GB, but stock sh3.exe only knows about 2GB RAM. Installing the 4 GB patch will let SH3 use more RAM, which GWX seems to really need. I suggest you try this first.
If that doesn't resolve your problem, try removing the hi-res fix. There might be an incompatibility with your hardware, or with Win8. The high res fix I am aware of was originally developed for Win XP/SP2, so may not work with your edition of Win8.
Please post your results.