Indesign CS5 won't Save or Save as..

I have recently installed Mac OSX 10.6.3  (snow_leopard) onto my iMac and now for some reason Indesign CS5 will not save or save as.

It allows me to selecteither of them in the menu but nothing happens at all. If i try to close the document after making changes it just closes without asking if i want to save and i lose all the changes.

I have also gone to the extent of doing a clean installation  of the OS & CS5 with no difference whatsoever.

Any ideas would be extremely helpful..

Thanks