Machine slows to crawl when printing

[Bruce]

I am not sure if this is a kprinter problem, but if I try to print
something out on my Epson Stylus C40UX at high resolution (1440x720)
(which can take an hour or more to print a full page), the machine will
become pretty much useless for anything else.

While something is printing, switching from one running program to another
will take 10-20 seconds; access to the internet is slow to the point it
isn't worth the bother (sometimes a few lines of text from a page will
load, but generally everthing, including fairly simple text pages, will
just time out) (this machine is connected to a LAN accessing the internet
through a DSL connection on a gateway, and the internet connection works
fine from other machines at the same time)).

The machine, though not the latest and greatest, is not particularly
underpowered for desktop use (Athlon 1.2, 256Mb RAM + swap), so not sure
why this happens. Lots of HD space.

Running KDE 3.1.2, using CUPS 1.1.9final, on up-to-date Debian
testing/unstable (installed from Knoppix).

Any suggestions on what could be causing this? I am not really sure what I
should be checking for troubleshooting. Or is this normal behaviour for
high-res printjobs on cheap printers?

Thanks,

Bruce