[mpalangio]

sorry for the htm formatting below might be earsier to read.

I have just corrected this problem on our server. Not saying for sure, but here is what your problem is. Your certificate is issued from an Intermediate Certification Authorities Ours was Go Daddy. You will need to install on your exchange server that active sync is syncing with, the intermediary root certificates and then perform an iisreset. Here is the go daddy link explaining this process with their certificate package link on the page.

http://help.godaddy.com/article/4875

if your certificate is not from godaddy then look in the help or Faq on their web site for something similar.

Hope this helps.