I ran into similar trouble with Hotmail - it would not let me in, and said my security was not properly configured. I think you need to make sure you have 128-bit security on your device. The link is REALLY hard to find - because Microsoft constantly re-directs you to the Embedded Windows site (AAARGH!!) I only stumbled on it when I had given up (the zen of WIndows)So go here, and download and install this security upgrade and see if that helps. You will also need to go to the pocket IE optoins and check in the boxes for security items.
http://www.microsoft.com/mobile/handheldpc/downloads/128bitSecurity/128bit.asp
Doug