I'm going to agree that the issue has been caused by Microsoft's early October update.  However, since Intuit utilizes Microsoft operating system for their software, it makes it a problem of Intuit to figure out what changed and why.

So far the issue seems to affect only select computers, so if you have an extra computer with the software installed you should consider using it until Intuit has learned why this isn't working right.

I haven't tried the last suggestion, but rolling Windows back to the September configuration might be a good choice too.

While I don't know why the error is occurring, I have found that running Homebase Maintenance will bring back the "deleted" client files.  It seems that restarting ProSeries is normally required as part of this process also.

Finally, I also experienced this making my main computer no longer findable on the peer to peer network.  Turning off the Network sharing settings in Advanced Networking and restarting the computer before turning these back on has dealt with this particular issue.

Again, it is definitely something that Microsoft has changed, and Intuit just needs to catchup with the computing world on it.