I tried the updated driver, no dice. Why does my 3Com 3c905B Ethernet card work STILL not work?

Two things you can try to fix this:

1. Disable Plug-and-Play in your PC's BIOS settings. Plug-and-Play often interferes with the BeOS's ability to detect and use various pieces of hardware.

2. Use the DOS-based configuration utility that came with your card (on the floppy disk with the DOS/Windows driver, most likely) to change the card's media type setting from "autodetect" to the actual media type to which it's connected (probably 10Base-T, these days).