i get these too- and suspiciously think it's Google not seeing any logins after bans from accounts with large spend histories and going "hmm- let's tease him with $100 off the old contact info we have <from the banned accounts> to get him to try and use it so we can figure out what his new accounts are"
It's very odd, given they're coming to strange addresses
I just got one the other day too and little to say I can't use it either...It's really only good if you haven't used adwords before.