While upgrading from Fedora7 to Fedora9 I had this recurring problem. To my suprise I had solved it before and forgot! Thanks for the archive! I looked up my previous solution of 2 years ago and it worked after some tweaking.
The environment:
The symptoms:
The solution:
It appears that the host MTU for its network adapter must be as large or larger as the guest's network bridge MTU. Better explained here:
A couple of tweaks:
Hope that helps,
Glen