If nscd runs, the package clamav-data often fails to create the user clamav. This is due to a negative clamav group query being cached when fedora-useradd is run. I would advice running nscd --invalidate=group between fedora-groupadd and fedora-useradd. Alternatively, fedora-usermgmt tools could be changed to invalidate nscd caches when necessary.
Thx, I modified fedora-usermgmt in version 0.8+ to do the 'nscd -i...'. This should fix this issue.