Hi OkieInCOS,
Sorry for the delay in response.
If you are still experiencing the issue, please try to repair the installation of the Adobe Acrobat XI.
To repair, open the Adobe Acrobat application and go to Help menu > Repair Installation.
Make sure that the application is updated to the latest patch released.
You may refer this help document for more information on updates: Release Notes | Adobe Acrobat, Reader
Also try once the troubleshooting steps provided here: Troubleshoot Windows system errors, freezes | Adobe software
If this does not help, try once to reset the preferences: How to reset Acrobat Preference settings to default.
Check if this helps.
Let us know if you have any question.
Regards,
Meenakshi