greetings...
 
> During the boot sequence, I get:
> 
> HP98643 (LAN) at 21 080009032844 Failed
> 
> and then it kinda sits there forever.  at the bottom of the screen, it
> claims to be "SEARCHING FOR A SYSTEM", but I think that the lan error is
> probably keeping it from doing that.

the error message ( it is indeed such a thing ) just tells you that the
boot PROM think's that it's LAN adapter is somehow broken. 
The message "SEARCHING FOR A SYSTEM" tells you that your machine just
probes around for bootable devices - HPIB, SCSI ( if you have it ) and
LAN ( if the PROM didn't disable this because of the error you mentioned
)

ok, answering your question: it should be a recoverable error. If you
have anything else you could boot from. maybe you should hook another
machine next to your 340 and have a look at what tcpdump says.

bye
Michael