Causes of router/switch hangs?

[Hewitt Tech]

Recently I ran into two similar situations (or at least similar symptoms at
two different client sites. In one case a LinkSys 24 port switch would
intermittently hang. Troubleshooting revealed that one particular connection
seemed to be causing the problem and the cable attached to the port was
fairly long probably 200+ feet. We decided to fix the problem by placing a
small switch approximately half way along the length of the run thinking
that the cable needed a repeater which the switch would essentially provide.
Within a few days despite our efforts the switch hung again (and the Linksys
switch was less than a week old when it got replaced).

In a second scenario, the customer had a 4 port Netgear DSL/Cable modem
router which hung. I reset the power and the Netgear unit came back on line
but as a precaution I decided to replace it. My question in both of these
situations is whether power or other environmental factors could result in a
hung router/switch? Possibilities that come to mind - dirty power (both
sites are medical facilities and although nothing appeared to be running
that could create noisy power, I don't know with 100% certainty that
somewhere in the facility a power hungry piece of equipment isn't cycling
on/off like an X-Ray machine for example). Another possibility that occurred
to me is that perhaps one of more of the Cat5 cables is laying next to a
power cable and noise is being induced in the line. Finally perhaps it is a
matter of firmware in the devices. Newer firmware might fix these kinds of
problems. My plan is to add a UPS at one site for the router but the first
site already had a decent UPS used to power the LinkSys switch.;

Any thoughts? How do we troubleshoot these kinds of problems? Scope the
cables perhaps?

-Alex