The symptom is as follows:
1. I swear copiously and re-install the OS.
2. I install all the applications.
3. I apply all service packs and patches.
4. I restore data from (fortunately recent) backup.
5. It runs OK till I accidentally flex the case (by, for example, moving my knee a quarter of an inch).
6. The laptop dies horribly.
7. When I reboot, crucial files are missing and it won't work.
8. I Swear copiously once more, and repeat from "1."
I'm going at about two reinstalls a day this week.
It works fine when it stays firmly on the table, where it is now. Ummm ... time to buy a new one.
Went to http://www.novatech.co.uk last night at 1am and spent all my worldly wealth.
New laptop to arrive in about five days -- I'll keep you all up to date with how I get on.