That would defy logic. Clearly, MP has not changed, thus, something else has: Windows itself, a setting on it, a 3rd party app, driver or policy on the work PC, etc.
It's possible, even likely, that any number of updates were installed on the secondary machine in the background. Unfortunately, due to the restrictions in place on the secondary machine, I don't have any reliable way to determine what updates may have been installed.
You would have needed Admin access to install it so can we assume you can readily request it?
I was able to get approval for the use of MP, but it was installed remotely by the systems admin rather than me being given even temporary admin access to the local machine. In short, I might be able to get the admin to remove and reinstall MP, but I don't know how likely that will be.
One thing I have noticed in the past couple of days, which may point to this being somehow network related, is that in seamless mode sometimes my mouse cursor "wanders" significantly when working on the secondary machine. Even if I remove my hand from the mouse, the cursor moves slowly around on the screen for a few seconds. I couldn't say entirely how long this may have been occurring, as I only recently started using seamless mode between these specific machines and it's not something that happens frequently.
I fully understand that my inability to get admin access on the secondary machine may leave me out of luck in troubleshooting this issue, so not to worry if the answer is "Sorry, can't help". 
Even with the mouse movement issue described above, seamless mode works well enough that I have no reason to stop using MP entirely; just would be nice if I could somehow get KVM back up and running.
