I don't know wether this is a bug in fetchmail or imap (both from Redhat Linux 6.1). The appended file contains a problem description and a patch I'll also upload the patched versions to contrib.redhat.com Joerg
Created attachment 40 [details] Problem describtion and possible fix
Thanks for the heads-up. This was incorporated into 5.2.1 the week after you filed this report. Newer versions of fetchmail are currently in Raw Hide, and are slated for inclusion in our next release.