I've installed the TF-Client on a computer with Office2003 ... all worked just fine. Then I upgraded to Office12 B1. Now Excel and Project have problems to connect to the server:
TF84034: Team Fundation was unable to initialize the workbook. This document will no longer be associated with a Team Foundation server:
TF80071: Team Foundation ecountered an error while accessing the work item database. Please contact the Team Foundation Server administrator.
I'v tried to install the client... no luck
Is TFS B3R not supporting Office12

TFS B3R and Office12
Klaus Revermann
Excel12 Beta2 will have the fix and will work with TFS.