After installing the January updates for Office Communications Server 2007 R2 and publishing the new Communicator update to Client Version Filtering, I received an error that my client could not find the update.
I looked in the IIS logs and noticed that it was trying to pull the update for the x64 architecture.
2010-01-10 21:11:12 192.168.200.151 POST /AutoUpdate/Ext/Handler/OCUpgrade.aspx folder=OC&lang=1033&mode=non-ui&arch=x64&flavor=pm&build=fre 443 - 192.168.200.70 Microsoft+Office+Communicator/3.0 401 2 5 596
Subsequently, my client was able to download and install the new Communicator update.
2010-01-10 21:34:53 192.168.200.151 HEAD /AutoUpdate/Ext/Files/OC/x64/fre/1033/Communicator.msp - 443 - 192.168.200.70 Microsoft+BITS/7.5 401 2 5 63