Vista network discovery and file sharing keeps turning itself off

[mrochester]

As per the above title, Vista keeps turning off network discovery and file sharing and I have no idea why. I find out that it has done when I open 'Network' and a bar pops up near to top of the screen informing me that it is switched off and inviting me to turn it on. But why won't it stay switched on?
Thanks for any help.

 

[mrochester]

Bump.