There may be some clue in that while I was briefly able to use the application I added a few picture files and put them on the timeline.
Tidying up the pictures on the pc into one folder meant that one of these was no longer where Premiere Elements 8 expected it to be and on one of my trys at getting it to run again (with the same multiple attempts at opening a project as before) it did actually display a dialog asking for the missing file and then wonder of wonders the monitor window, timeline, etc, appeared as before.
This meant that the menus are accessible at present and so I've been able to check the background rendering preference and it is set to off.
Once I close the application down again I'm sure it's going to behave as before, ie blank screen again. True enough just tried this and it's back to blank screen mode. I didn't save the project so the files are still 'missing'.
BTW I've already turned off Autoanalyse in the Organiser.
Assuming you've gone to Windows Update and downloaded even the optional updates (brand new computers are 4-6 monts out of date) and that you've cleared off your tmp files and defragmented and downloaded the latest version of Quicktime from Apple.com -- it may be time to call Adobe Tech Support. You likely need some pretty specific troubleshooting, too much for us to walk you through it on these forums.
Work through the PRE troubleshooter to see if that helps: Troubleshoot damaged projects | Adobe Premiere Elements, Troubleshoot ...
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Thanks I'll check this out and contact Tech Support if I still have problems after this. BTW Quicktime, Windows updates, system maintenance, etc, are all up to date.
Thanks for your suggestions. The laptop is automatically updated. Quicktime is
up to date and so on. I'll contact Adobe next week.