webmatrix has stopped working

Hi

Just reinstalled Windows 7, Expression Web and WebMatrix and now I'm getting an error whilst trying to use WebMatrix. I can start Webmatrix and open a saved website but if I then touch anything like 'Files' it stops working and a message tells me that 'WebMatrix has stopped working'.

I have never had problems with WebMatrix before so how can we fix this problem as I like using it to develop WordPress websites?

Thanks

Colin