hey all, i've done it now. Yes i run a mac of course with osx and was an upgrade from cs3 to cs6. i ran the upgrade and then removed the cs3 applications which cause some of the cs6 programmes to not load correctly.
so removed cs6 and re-installed and now all is working fine!
It's not as simple as dragging the application to the 'trash' icon. It leaves behind a load of unused files in weird locations that clog up the system. Best to run the uninstaller or get an application that does that sort of thing.
And I assume you've already done it by now but I would have upgraded the Mac core before updating all the program's. It just makes sense to do it that way.