License activation has stopped working

I have activated CrossWorks and have been using it for some time but today it stopped working and I am getting a "No installed licenses..." error. What could have caused this?

The most likely causes are:

• You are using an evaluation licence and it has expired.
• Your hardware has changed. CrossWorks is locked to your hardware, if it has changed you will need to request a new activation key using the product key you were given when you purchased CrossWorks.
• There is a problem with the clock on your PC, check the date and time are correct.