avahi-compat-howl-devel and avahi-compat-libdns_sd-devel to not depend on avahi-compat-howl and avahi-compat-libdns_sd respectively. This causes a devel pacakage that's insufficient to link a user of the libs to be installed.
fixed with avahi-0.6.11-1.{fc5,fc6}
avahi-0.6.11-1.fc5 has been pushed for fc5, which should resolve this issue. If these problems are still present in this version, then please make note of it in this bug report.
Confirmed.