I have been unable to play games that I have purchased on Gog against otrher individuals in Game Ranger. The issue I face with Nox is that on the rare occasion that I do discover my friend's hosted game I get an error message telling me that my files are corrupted. My knowledge of how to fix this problem is limited and was curious if anyone could help me understand and/or fix this issue.

Thanks...

I've never used Game Ranger, but I suppose that the software checks games' version for compatibility reasons. Probably the GOG version is different from the original one, due to the removal of DRM, so GR thinks that your files are corrupt.

You can also try this fix.

Playing in gameranger is not recommended. Better play in westwood online.