This seems to be a known issue with the Broadcom 802.11b/g in HP laptops. If you successfully flashed your BIOS and still have the problem you may want to contact HP and request a replacement wifi card or service to be done on the laptop. It seems that this wifi card may have a design problem.

Check also:

Vista Freezes Solid Trying to Connect to Some Wireless Nets - CNET Wireless Internet Forums