Although we all wish this wasn't the case, bugs do slip through the cracks from time to time. We recently found a memory leak issue in the Enterprise Library Configuration Application Block, which is used by all of the other blocks. The good news is we have a fix (called Patch 1475) and it's limited to a single source file so it's very easy to patch. I'd like to encourage all users of Enterprise Library to go to the community site and download the patch (note you need to join the community to get the patch, but don't worry, everybody is welcome!).
We will also be releasing a minor update of the entire Enterprise Library package that incorporates this patch and the previous one, but this will take a while to get ready so you should grab the patch now to make sure you aren't exposed to this issue.
BTW don't get scared by the name Patch 1475. We haven't released that many patches (in fact, only 3, and the second included everything from the first). 1475 is actually an internal tracking number.