[Hampshire] ?on topic, ?OT? Synaptic/apt/repository problem…

i have a problem with Synaptic on a new install of PCLinuxOS MiniMe 2008.

Initially both Synaptic worked fine.

Then it worked fine most of the time, and I was able to use apt-get when it
didn't.

I moved it and Synaptic and apt-get started to break down.

First I couldn't reload/update - on either, saying that the repositories were
inaccessible. So of course I couldn't load any software.

I suspected that the router had some strange setting in its firewall, but
couldn't find one. Then Synaptic briefly worked - for long enough to reload
half the files. After which half the GUI display disappeared. (I could no
longer show uninstalled programs.)

Now I have moved the computer back to the original router, and things are even
worse. Synaptic can no longer display and edit the repositories. The
sources.list is still intact and can be edited, but to no avail. Synaptic
will display even less and both apt-get and Synaptic are still broken.
(Well, apt-get is fine except that it cannot reach the repositories.)

The repositories are fine. I can access them from another computer using the
same distro and running on the same router, and everything works fine.

Help!

I suspect hardware. But I have already taken the box back to the shop and
been told that it was viruses. I didn't think so then and I don't think so
now. I don't think that the shop ran any hardware tests. I unfortunately
suspect the motherboard (from the previous history of the box). Possibly the
IDE slots.

I shall run Memtest 86 overnight, but is there anything else with respect to
either software or hardware that anyone would recommend?

Thanks!
Lisi