Unable to log in to KDE4 using Hardy

[Rosalind Mitchell]

I tried installing KDE4 to evaluate under Hardy.

I log in correctly at the usual prompt, selecting KDE4 as the chosen session.  
A KDE4 splash screen appears.  The usual series of icons appears as it goes 
through the motions of setting up, and then...

Back to the login prompt.

So, clearly something is wrong.  Has anybody seen this before?  And is there a 
way I can get a trace of the progress of the login sequence?

Rosie

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