My PDF's once opened closee for no reason in about 20 seconds. Well there is a reason and I'm trying to find out. I installed XI Pro recently from a DVD permenant license and this is now occurring.

Hi, ​@quirky_video8dec, My guess, without much information, is that your new computer and/or the computer’s OS is not compatible with Acrobat XI.

Here’s what I find on the internet:

 

• Windows: Windows 7 (32-bit/64-bit), Windows 8 (32-bit/64-bit), and Windows Server 2008 R2, 2012, or 2012 R2.

• Mac: Mac OS X v10.6.4, v10.7.2, or v10.8 (Mountain Lion)
  
  If you are not using those OSs, you’ll need to downgrade your OS or upgrade your Acrobat. 
  
  Sorry