Hi Test123451,
There have been issues where the users profile gets corrupted. This can be resolved by deleting the profile information (it gets rebuilt the next time Designer is launched). The location of the profile will be based on the operating system. In my case (I am running Win 7) my profile will be:
C:\Users\trkumar\AppData\Roaming\Adobe\Designer\10.0
Simply delete this folder and you should be OK.
Hope that helps
Regards,
Ravi