After further investigation, I have found the update culprit to be KB980232. As I mentioned in my question we were having problems saving across the network.
What I failed to mention is that the server in question is running NT. It appears that this update does not support NT.
Once the update was removed from users pc's, they were able to save across the network again. I can only hope that a KB version will be released to support
NT, or I'll have to leave some pc's unpatched for this vuneralbility. As a sidenote: when I uninstalled KB980232, it also uninstalled KB976323 and KB979683.
These are also vuneralbility updates. I'll try to reinstall them separately.