Screensaver not working automatically

[Joe Hart]

Nigel Ridley wrote:
>>> The problem is is that the screensaver does not start automatically 
>>> [after the set time]. If I 'lock' the screen then the screensaver 
>>> does work.
> No, it's 3.5.2 as is all the other computers that don't have the same 
> problem.

Strange.  Sounds like a video driver problem. 

Which video card and driver are you using?

If you open another tty (ctrl-alt-f2 for example) when you come back to 
X (ctrl-alt-f7) does it work?