I am currently having a very similar sounding problem with SHIII GWX on my recently upgraded system. I used to have a socket A sempron 3000+ with sata HDD and 2 Gb DDR. I though it would be a great idea to upgrade to an AM2 system with DDRII 800. Unfortunately not as things turned out.
My system:
AM2 AMD 64 Athlon 3200+
X2 Gb DDRII
ATI X800 XT
Audigy 2
MSI MB
X2 Maxtor SATA 1.50 Gb/s HDD.
The dvd, GWX setup files, mods and patches are exactly the same ones I used when I installed the game on my old system on which everything worked fine. Now, after between 30sec and four minutes, the whole system locks up completely. I thought this might just be a problem with the GWX installation or possibly some of the mods, but I have tried the stock 'vanilla' game with and without the 1.4b patch, sadly with the same result.
I have replaced all the GXW and mod files from different download sites incase they were corrupted. Both the HDD which I have tried the game on have been reformatted. I even went to the extent of stripping the system down and reassembling it and replacing the sata data cables. No improvement.
I thought possibly my Zone Alarm might be responsible, but it had caused no problems on my socket A system, so I couldn't see why it would start now. But I tried a fresh SHIII/GWXC installation after first uninstalling and stripping out any and all ZA files. With no improvement either. I have updated my MB chipset drivers, tried eight different versions of the Omega drivers, even though they worked fine on the old system. All my other games work fine such as Tomb Raider Legend, Myst 4 and 5 and others, no problems at all. The rest of the time my system works fine, no issues at all with any other applications or software. The O.S has been reloaded three times just in case.
Right the way through from vanilla to fully patched and modded GWX 1.03 the lock ups continued.
Is it just that SHIII/ GWX is incompatable with my system somehow or is there any way of fixing this. Please.......anyone