Remote connection failed for mysql (no replies)

We have two environment - Production and Testing, they both are running 5.1.44-ndb-7.1.4b-cluster-gpl under RHEl 5.4.

Both environment's mysql server running smoothly in the past few months. However few days ago we have restarted the prodcution environment. The following error message is observed in the log file when there is a remote connection. Remote appications are not able connecting to mysql server:

110106 15:53:30 [Warning] IP address '10.0.11.1' could not be resolved: getnameinfo() returned error (code: -3).
110106 15:53:50 [Warning] IP address '10.0.11.5' could not be resolved: getnameinfo() returned error (code: -3).

We didn't make any configuration change. After this error message found, we have changed the my.cnf and add the line skip-name-resolve. The problem is solved after that.

We are confused that while the Testing environment having the same configuration as production one, it didn't encounter the error like that. And this error happen after mysql restarted over half day.

We have no idea on explaining why the above scenario will happen. Does anyone experience that before?

Thanks.