I have a Global Village fax modem on my PowerBook. I'm constantly getting Type 1 errors. I've done a clean install of system software, and ran Disk First Aid. When I fax using the Global Village software it goes through, but then the document becomes corrupted. This doesn't happen with the LaserWriter driver 7.2, only with the 8.0 driver.
This is a known problem and has been fixed in the LaserWriter driver version 8.1.1 and all LaserWriter drivers released after v8.1.1.