Problem solved ... kind of.

WCG will allow me to attach to MY account but not to someone else's account .... most of the time. I do have a laptop I've never used for crunching WCG so I attached using the other account login. It creates a file in the BOINC directory called "account_www.worldcommunitygrid.org".

On the machines that wouldn't connect properly I shut down BOINC and copied that file from the laptop to the main cruncher's BOINC directory. When I started BOINC on the cruncher it shows that it is attaching to WCG. Everything works as expected then.

I still don't know what is causing this, but there is at least a work around. I didn't look at that file all that closely but it appears that you "strong" account key is embedded right at the beginning. You might be able to just change that to move from account to account.