This generated a lot of mail. One reader (Jan Rune Holmevik) confirmed this for his PowerPort PC Card in her Powerbook 5300cs running Mac OS 7.6. However, many more readers (including Joel Sass, Dana Rasmussen and David Webb) said that it definitely did not fix the problem for them. One reader said it was never intended as a bug fix anyway, but only to provide the 33.6 bps feature. None of the standard work-arounds (changing the loading order of the Toolbox extension etc.) had any effect on the bug.
However, Joel found that if he simply added a space in front of the file name "Open Tpt AppleTalk Library," the problem went away. Deleting this file (as well as "OpenTptAppleTalkLib") also helped - but you then lose AppleTalk access.
Speaking of PC card 33.6 bps upgrades, there now one for the TDK Global Class 2814 Apple Powerbook Data/FAX Modem PC Card. Get it at the TDK web site.