Whether I am trying to merge tags or simply rename a tag to a new unique name every tag rename results in the error, "An error occurred while testing for the new tag name."

I am running MT 4.0 at Dreamhost with only these plugins in addition to those that came with my install:

- FeedburnerWidget 0.1
- GoogleAnalyticsWidget 0.1
- Refeed 1.0

I'm seeing this exact same error, with only the Enclosures and Better File Upload plugins installed.

Same problem here with MT 4.1. When I try to rename tags from "Manage tags", I get the above error. This happens only with few tags and not all. I tried even to remove them and add them again, but it seems that the exact problematic tags will have problem after creating them again.
Is there anyone who knows if there is a bug report for this in the fogbugz? Do you know what can cause this problem? All the privileges are set correctly in DB. Moreover, do you know how to register for an account on Fogbugz?

Thanks.

I have this problem as well - judging by the number of people with thjs issue it seems to be either a problem with the code or a common configuration issue. Hopefully an answer will be forthcoming. FWIW I've had this problem with both 4.01 and 4.1.