I kept getting MSExchange ActiveSync 1040 warning events on many client’s Exchange servers (2003 and 2007). The event itself sent me to http://support.microsoft.com/kb/905013 (thanks Microsoft, that does help!) which pointed to a firewall issue.
Since we are using Cisco routers at these sites, I did a quick Google and turned up nothing. Darn, time to hit the books 
I threw the following command in to modify the timeout in the CBAC inspect of HTTPS. I set the timeout to 10 minutes.
ip inspect name <inspectname> https timeout 600
So far the warning event hasn’t shown back up…
