I tried applying the 1.4 patch (thanks CDNMerlin!) to the GoG version, but I got the 'Wrong Save File' error. I deleted the install, restarted, and tried it clean but no luck.
This thread mentions the problem, and a possible solution is to apply the UK 1.3 patch first. That's proving to be a tougher one to find so far.
I'm running it on Windows 8.1 64-bit, Intel i3 2120T, 8GB memory.
I may put this aside for now and hope that when the Interplay site comes back, it'll still host those patches.