Upgrade to Kde 4.2 > nothing but blank desktop

[richard terry <rterry@xxxxxxxxxxxxxx>]

I upgraded from 4.0 (which was sort-of-functional) to 4.2 this morning and on 
loading the kde desktop has nothing on it, dosn't respond to any keypresses.

I created a new user, tried again> same thing.

Any clues for a clueless user as to where to start?

Regards

Richard