> But I don't see how ppp would be different hardware-wise.

It shouldn't be.  I suspect it's a flow-control problem.
Sean: I would make sure that the connection looks good and can pass text
with kermit running on both sides with the same settings:
	set speed 9600				equiv. to pppd 9600
	set flow-control rts/cts		equiv. to pppd crtscts
	set carrier-watch off			equiv. to pppd local

-allen