> There are two separate problems. One of them is dropped
> characters. It happens about once a page or so. Yes, the cable is
> attached firmly, it's short enough, and it's shielded.

I have had the first problem and not the second one.  I
suspect dropped chars has to do with faulty flow control
implementation in the driver.

Try using the polled driver (as someone else noted) and see
if the dropped chars drop out.

> The other problem is that every once in a while my system comes
> to a complete, dead, halt. Nothing works short of the Big Red
> Switch.

You mean you can't even get in the debuger by hittin ctl-
alt-esc?  If you can do that and find out where the kernel
is hung perhaps someone else can figure out why.