For anyone with an IBM Thinkpad (I have the 390e) that uses a Texas Instruments Cardbus controller (old or new I believe), the Linksys WPC54G works great with the new beta driver found here:
ftp://ftp.linksys.com/beta/wpc54g_beta_driver.zip .
Linksys was obviously aware that there was a problem and it looks like they have corrected it. Props to Linksys, but I will continue to test it out and report back here.