What OS are you using?
I wouldn't run CS 5.5 on any operating system newer than Windows 7 or Mac OSX Mavericks. If it's a really new OS, you're just asking for trouble.
thanks Dave for replying - I am on Windows 7 on a pc.
Have been experimenting and found some strange things happening...opened old AE projects from a few years ago and motion sketch worked fine.
Then when I open a new project it doesn't work...but if I check the Show Background box it works...I am bamboozled! An odd glitch????????
Will keep playing with it and see if there is a pattern.
I will be staring on a new project soon so need to know that I can just get to work without pfaffing about with it.
Hiya Szalam see my reply to Dave.
Thanks for your reply.