Frequent lockups - the resolution?

[brian]

Thanks to all for the many suggestions. I'm fairly sure it wasn't a
'dirty PC' problem, as I do keep the fans clean, and running the
sensors for a while didn't show anything untoward. 

I gave building my own XFCE 4.12 a try, but gave up on that - there
are just too many version problems with vanilla Debian Jessie, i.e.
newer versions of libraries required. I think 4.12 under Debian is
going to need Sid, and while I did successfully upgrade to that in a
virtual machine, the sheer volume of updates causes me problems due to
the satellite internet connection, as I've said previously. 

So where do I stand with the problem? Well, the switch to Chromium
**appears** for the moment (frantically trying to get round Sod's
Law!) to have cured the problem. I can't believe that it's a simple
bug with Iceweasel and Jessie that has remained undiscovered for this
long, I have to think it's one of those goofy multi-way interactions
involving two or more pieces of software which *together* create the
problem. Possibly using WINE applications doesn't help, but I've two
Windows applications (my mailer/newsreader being one of them) which
I've found absolutely nothing to equal in the Linux world, so WINE is
an essential for me. 

In short, I don't think I'm going to find the answer, but I think XFCE
is probably in the clear. :) (It may be part of a multi-way problem,
of course). 

As long as Chromium keeps running reliably - and yes, I did have a
couple of crashes with it, but none since I made the original post -
then I'm going to leave well alone. 

Thanks again for the ideas, everyone. 

Brian.