Are you 100% sure you are connected to the Internet? Are you able to check email, login to instant messaging, etc.? Have you tried power cycling your device and clearing out temp files, etc.?
Also, double check your settings to see if you have everything configured correctly.
Take a look at this wifi guide for Ipaqs:
Wireless Settings
Note that it is written for WM2003 so it might be slightly different if you are running WM5.