On 08.09.2013 05:23, I wrote:
An exit relay that has just been updated to 0.2.4.17-rc produced this message
Sep 07 19:59:30.996 [Warning] Your Guard maisterikaarna ($C3B7CC79FD4E302AF8956A7B02F0FC7AAB4A6AF8) is failing a very large amount of circuits. Most likely this means the Tor network is overloaded, but it could also mean an attack against you or potentially the guard itself. Success counts are 52/151. Use counts are 0/0. 52 circuits completed, 0 were unusable, 0 collapsed, and 1 timed out. For reference, your timeout cutoff is 142 seconds.
I guess the part about the Tor network being overloaded is/was true, because my non-exit relay got a similar message at that time.
Strange thing though: my relay only used about half of it's bandwidth at the time.
-Stephan