Annoying error/bug

Sat Apr 24 17:33:46 UTC 2010

Every time I startup my part-time relay I get this error after ~2 hours, 
running 0.2.1.25 on Windows server 2003.

Apr 24 10:50:48.426 [Notice] Self-testing indicates your ORPort is 
reachable from the outside. Excellent. Publishing server descriptor.
Apr 24 10:54:25.448 [Notice] Performing bandwidth self-test...done.
Apr 24 12:48:24.863 [Warning] We just marked ourself as down. Are your 
external addresses reachable?

Can someone tell me who/what is generating this error and why?
And yes, my relay is reachable.