I strongly suggest you do not roll-back the firmware but try and stay current with it. A case could have been made with the 1.44 firmware for the BEFSR41, but has ceased to be an issue with the 1.44.2 release of the firmware.
As for your XP problems the fact that you have had problems both with 802.11b and 802.11g cards suggests something else besides firmware is at issue.
The three big "gotchas" of XP and wireless adapter:
1. Disable 802.1x authentication. It is very rare that it is in fact supported by your wireless adapter; wait for WAP, use WEP.
2. Wireless Zero Configuration. Some turn it off and wonder why their adapter will not work. Some use the included wireless client and have wireless zero configuration enabled. You cannot mix these states. Enable Wireless Zero Configuration, and do NOT use or install the configuration client. There are some exceptions, but this is a good very general rule.
3. Software stubs. As a very, very good general rule the un-installation routines for wireless products is just awful in cleaning up after an installation. I cringe to hear that someone tried brand X, returned it, and now cannot get brand Y to work either. It is not unusual to find two or three wireless clients being loaded, numerous .dlls from other clients, multiple drivers from various clients, etc.. I strongly urge a good un-install program be run prior to installing any wireless adapter software. Or, in the alternative, freeware utilities that monitor registry and file system changes. Or, at the bare minimum print out the .sys, .dll, .inf, .cfg, and .exe listing of all subdirectories on the installation disk and if you decide to change brands do a search for each one and manually remove them. Then search the registry for "Linksys" or "Dlink" or "Buffalo" or whatever is appropriate and delete the entries.
One last "gotcha" that is sometimes a factor in laptop/notebooks is the use of chipset specific cardbus controller drivers. I have had much better success under XP changing TI-specific drivers under Device Manager to Microsoft's "Generic Cardbus Controller" drivers. Linksys, for one, is now offering a TI-chipset specific driver for its 54g wireless card adapters.
I have been very happy with 802.11b under XP, and generally pleased with 802.11g, a work in process. The 802.11a implementations I have tried had range problems that made them unsuitable in my case, but worked as advertised under XP for me.
Best to all.