I have no idea what the cause could be.
Assuming you have windows of some kind - It would be nice to give basic info about your system to assist members help you......
Never mind - no such info exists so I'm forced to guess a bit
I'd probably suspect something was wrong with registry so a search of this forum revealed a possible cause and solution
http://www.digitalgrapevine.info/viewtopic.php?t=3221&highlight=reset+registry
Have a look at that and see what you make of it.
The other thing is that your download could have a corruption. Have you re-downloaded it to see?
Good luck
Graham