Yeah, I can't say 100% that the VM doesn't have anything to do with the problems, because VMs do have unique drivers, but given that the game proper works just fine it seems unlikely to be the cause.
Yeah, it sounds like a folder pemissions problem, or at least i can't think of anything else that would cause the crash when trying to save.
The new Data folder you created in the new directory to where you copied the game files. Have you checked it's not set as 'read only' aswell ?
I just installed gog's version of Riven on my Win7 Ultimate 64bit machine to check out this save problem, and i'm not experiencing it.
-Right clicked the installer to run it as admin,
-Installed the game to the default location,
-Right clicked Riven's shortcut to run it as admin,
And that was it. I can save and load whitout any problems and as far as i can tell everything is working as it should.