1script - 2:37 am on Sep 21, 2012 (gmt 0)
No remedy but perhaps it will make you feel a little better: you are not alone! I'm getting the same notifications on a number of sites in my account and what they say is certainly not true: not only DNS was up all the time but also, why other sites, also served by the same DNS server, are not affected?
The funny part is: if 1 error is 50% of all attempts, then they only tried to load 2 pages from that site on that day? That's a bit too low for Googlebot, no matter how small and even how badly penalized the site it.