Its probably a capability issue with your PDA's browser.
In your PDA, goto
www.operamini.com and download the free browser for your PDA. Then use this to access your mail.
The Opera Mini browser (especially the version 4 beta which is also available from the same site) is very good and works for most things on my PDA when the built in IE fails.
In fact, if im being honest, i use this now instead of IE on my PDA for all browsing.