Tried again today... same result. I find it hard to believe I am the only one having problems like this ? It's just a "normal" as can be Vista installation, that is 99.99% stable fully patched and up to date.
Managed to submit a free support request to MS, and that ran an add on diagnostic/data gathering tool so will see what the outcome is.
If I didn't know how to boot into safe mode, and didn't have an image backup it would be a really serious matter.
So it's Acronis time (again)