Disk Problems: Advice Welcome

[RGH]

I've been having some strange, but fairly predictable, problems with the
disks in my system. If disk activity is very heavy for a long
time---say, I'm downloading a lot of stuff---then, at some point, I
start to get disk errors and the system will all but freeze up. The
first sign is often an error from syslogd, saying it can't write to the
log, but I can also get similar errors from (e.g.) akregator, saying it
can't write to some file under $HOME. Other operations may continue to
function at this time: E.g., the download will continue, and I can even
start another one. But attempts to run commands can abort with
"Input/Output error"---though not all commands may show this problem.

This looks to me like some kind of hardware issue, but I'm not
experienced here. Any advice welcome, especially concerning what I might
do, other than replace the (expensive WD Raptor) disk.

Richard