Severe performance penalty after upgrade to 4.1

We just upgraded from 4.0.1 to 4.1.0 and one of our test suites went from about 5 minutes to almost half an hour! The test suite is rather large so its already slow, and this extra time makes it impossible to run during the day.

I have downgraded two installations to 4.0.1 and the runtime went back to normal. I upgraded the installations again to 4.1.0 and the problem was reintroduced. Therefore, we have now downgraded all our installations.

Please advise.

Regards,
Brian Rasmussen