Adobe Acrobat X Pro (10) won't start or launch - Windows

1. Make sure you are connected to the internet.
2. Launch a regular  CS6 product other than Acrobat or Flash Builder (for example: Photoshop, After Effects, Premier Pro, InDesign, Flash Professional, Illustrator, Dreamweaver.)
3. Click on Help->Deactivate .
4. Deactivate the application. Quit application.
5. Launch a regular  CS6 product other than Acrobat or Flash Builder (for example: Photoshop, After Effects, Premier Pro, InDesign, Flash Professional, Illustrator, Dreamweaver.)
6. Accept Eula.
7. Register trial by signing in. Let the app launch.
8. Quit and relaunch the app. Wait for UI to come.
9. Click on License This Software button on the UI.
10. Click on Sign in .
11. Serial number screen will come
12. Enter the serial number in the serial number screen and click Next.
13. Quit app and relaunch the app while connected on the internet .

After this if you launch Acrobat it will launch and run forever without trouble. In case you still face a problem, try relaunching the other CS6 app once more and then launch Acrobat. 

Originally from: http://forums.adobe.com/message/4491141