SolidWorks 2010 is not responding

I upgraded my OS to Windows 7 and then installed SolidWorks 2010 for doing my work. And then, I upgraded to SW2011 for a client. Since then, I started receiving a message:

SldWorks
SldWorks is not responding
Windows is checking for a solution to the problem…
Cancel
I could not access my work and the program just stops on responding. When I click on the Cancel button, the message will just disappear and then I have to restart my computer to access it again.
What seems to be the problem?
What should I do?
