Do you have the A05 ROM update? Although it caused some issues with WMP 10 (if people attempted more than a PIM restore, such as a complete back-up), it was a significant update for wi-fi as well.
And the traditional but true question: did you disable power management with Wi-fi?
Ikehiker is the wi-fi guru here. If you can't figure it out after these two items, read the wi-fi guide on the front of Aximsite...
http://wifi.aximsite.com/
and then contact IkeHiker through PM if the problem still exists.