I looked up in http://helpx.adobe.com/creative-suite/kb/acrobat-failed-launch-30-days .html for a solution in WHY my acrobat X pro is not lauching anymore and found this procedure: but this applies to a newly installed CS6 just after 30 days but I have now CS6 (and acrobat X included) working for months and again acrobat does not start, this is not the first time I reported the problem and again I have to deactivate/activate the entire CS6. This is NOT A SATISFYING SOLUTION
Important: It's necessary to perform the following instructions when connected to the Internet. Select a following product when requested to launch a CS6 Suite product: Photoshop, After Effects, Adobe Premiere Pro, InDesign, Flash Professional, Illustrator, and Dreamweaver.
To permanently resolve this issue, update all of your CS6 applications via the Adobe Application Manager.
[moving to Downloading, Installing & Setting Up forum]
I'm sorry that you're running into trouble with your CS6 installation. Please be sure to follow the last step on this document and update all of your CS6 applications via the Adobe Application Manager. The updates contain a patch to prevent this issue from happening again.
We've Launched a new hot fix for the Same. Please try it.
Here' the Link to Download it : http://helpx.adobe.com/creative-suite/kb/acrobat-failed-launch-30-days .html
If Acrobat previously installed on this computer where you installed CS6 and it says serial number exeeds maximum use when launch Acrobat, do the following.
Goto C:\Program Files (x86)\Common Files\Adobe\Adobe PCD\cache and delete cache.db file.
Launch any CS6 product other than Acrobat and activate -> Close the product -> Launch Acrobat.
You are done.
Thanks to Adobe technical support