I just noticed the same thing on my system. I was running .161 and when I launched it today, I got the message about the license (and trial period).
I have had networking problems at home for the last week or so (XP boxes seeing/sometimes not seeing each other and not allowing access to shared folders), so I've been changing box names and workgroups in troubleshooting.
I agree with eruji: I don't believe we should "lose" a license restore on something as simple as workgroup and machine name changes (although I completely understand the implications such actions might have). I have to wonder if I used my laptop at work (as I have in the past) under a different domain name, would that blow my license everytime I brought it back home . . . ?
Surely, there are other parameters that MC can check to ensure that it is not being pirated. Or at the very least, remember prior workstation and workgroup/domain name combinations so that if you roll back, so will MC.
I'll be sure to change my workgroup back BEFORE I restore the license and hope that it's not necessary to change it again in resolving the network issue.
Tbone