Msg#: 4628145 posted 7:14 pm on Dec 5, 2013 (gmt 0)
Probably not. It could be a fake (it's easy to spoof an email address - hopefully you didn't click on a link from the email) If you don't see any in your account, and you're not seeing anything unusual in GWT you're probably fine.
AdSense knows their crawl error stuff is out of whack, and I have been told by someone in support that they will be working on improving it after the new year.
Msg#: 4628145 posted 7:26 pm on Dec 5, 2013 (gmt 0)
I got that email today too. Funny thing is that there is normally some things listed in that report for me and today it was blank. I think the glitch this AM may have affected that report and this email just had the bad timing to go out when the report was broken.