Ooops, there are several reasons for this error other than the obvious. If you still encounter this problem after increasing your rollback segments, then there must be other causes.
Here's a list of the causes of this error.
Cause Description
----- -----------
1 A long query takes place at the same time as an update
2 Read consistent view during "insert"
3 Delayed block cleanout on old committed updates
4 Fetch across commit
5 Rollback segment corruption
You can search technet for white papers on this one.
Robbie
"The rule is, not to besiege walled cities if it can possibly be avoided" -- Art of War