Interesting Gnome window manager problem - Help

[Da Rock]

On the weekend I did some updates which were required and when I logged
back in I couldn't get the window manager working- which means I have no
window borders and creates any number of problems (which if anyone has
lost their borders would know).

1. Has anyone else had this problem?
2. Where the hell do I start to fix this?

I tried reinstalling Gnome with some disastrous consequences (overcome
now obviously as now I am emailing again.)- still no luck. And I can't
find a window manager as such for Gnome, so this is why haven't been
able to track it. And why would it come up after the updates?

Any ideas?