CERTCHK will not work on WM5 devices. I had the same problem when I rebuilt my Exchange 2003 SP2 server at home and it took me a while before I remembered what the problem was.
Exchange ActiveSync has a problem when using SSL and Forms Authentication. I did not want to turn this off as I use the FA for OWA. The workaround is to create a new Virtual IIS directory on the Exchange server which doesn't have SSL configured - see
http://www.petri.co.il/problems_with...activesync.htm (method #3) for more details. This article taken from one on the Microsoft website but I don't have the URL to hand.
I still have SSL between my X51v and my ISA server though which works well.
Regards,
Stewart
PS. Just found the URL from the Microsoft article:
http://support.microsoft.com/Default.aspx?kbid=817379