Not sure how well the subject line describes my issue. I have one user who can't connect to the exchange server using outlook (2003 or 2007) from any computer. I have set him up on a brand new machine with a new profile and he gets the "Can't open default folders" error. I've tried every encryption setting available on the client machines.
The problem appears to be affecting his mailbox, not any particular workstation or outlook installation.
OWA works just fine with his account from any machine. Activesync is also fine on his Iphone.
It may have become broken when he was using an older ipsec VPN on an unreliable connection which may have caused his connection to exchange to drop and try to reconnect. It's been happening for a few weeks now.
Any ideas?