I have similar problems with my BES setup
BES 5.0 SP1 running on windows 2008 x64
Exchange 2007 SP2, also on windows 2008 x 84
Globla catalog servers windows 2008 x64 and windows 2003 R2
first I ran through KB16118
KB16118-How to turn on global catalog referrals for a Microsoft Exchange Server
I made the registry changes to improve GC referral handling but to my surprise the registrey keys revert themselves back to origional values
now I stumbled onto this post
BES NIC has indeed RSS enabled, i will disbale this feature and see how it goes