Adobe Media Encoder - AMT Subsystem Error

When trying to open the application, I get this message:

"AMT Subsystem Error

Thank you for using Adobe Media Encoder CS6. The Adobe product that

installed Media Encoder has not activated.

Please launch and activate that Adobe product before continuing to use

Media Encoder."

All other applications are working, Media Encoder is the only application which has this error.

Not sure where to go from here, any suggestions are welcome.

Thanks!