At last! I found the solution to Active-stink complaining about an invalid SSL certificate during server sync (my company uses wildcard certificates - not supported on WM5).
Surprisingly (or not), the registry on Windows Mobile devices is very familiar if you have ever looked at the registry on a regular PC. Anyways, to disable Cert Checking, you navigate to the following location:
Hkey_Current_User\Software\Microsoft\ActiveSync\Partners
Here you should notice 2 sub-keys, both with a unique UID. One is set up for the ActiveSync Partnership with your PC, the other is set up for the partnership with your Exchange server. Fortunately, it is fairly easy to distinguish between the two. Simply highlight one of them, and look at the different values. You'll see pretty quickly which one is for your Exchange server. While the partner key for your Exchange server is highlighted, create a new value with the following
parameters
Type: DWORD
Name: secure
Value: 0
Thanks to Ben Winzenz, you saved me going bald dude.
http://winzenz.blogspot.com/2006/03/hacking-your-windows-mobile-50.html