I don't know. The office PC is connected to the Internet via the same server that connects the two Ubuntu PCs, which as far as I know have not been having any problems connecting to the Internet recently.
Does the office PC have Internet problems more often? When it does have a problem, does restarting Windows fix it?
At first thought, it seems unlikely that losing Internet would be a problem with Windows, but there haven't been any server problems lately that I know of. Is there any piece of hardware in the chain between the server and the office PC, like a router or something? That could be our suspect. I'll see what I can find out next time I'm around.