Acrobat Closing a PDF causes DO to delay responding

Help! I Need Somebody, Not Just anybody, Help! (sang at the tune of The Beatles song with the similar title)
First, Directory opus is my standard File Manager in my Windows 8.1 Pro Enterprise Edition. Here is my problem: EVERY TIME I open a PDF file using Adobe Acrobat Pro (v11.0.8) which is the latest version as of August 2014, and then I close it, Directory Opus takes a long time (about 40 sec more or less) to respond. It just stays there unresponsive. It's unbelievably annoying since I open hundreds of PDF daily.
Does anyone have an idea of what might be causing this?

Which version of Opus?

Does the same happen in Explorer?

Hey Leo. THANK YOU! for picking this issue up. The issue starting happening with the latest OFFICIAL released version of D.O. (version 11.5) Then I started reading the current betas and the fixes in production, etc. Then I thought that perhaps one of these betas might address the issue. As a result, I updated to 11.5.2, then to .3, then .6 and just now I downloaded (and plan to install 11.5.7 Beta as soon as I finish typing this post.)
As far as your question if it happens in Windows Explorer, honestly I have no clue. It's been years since the last time I ever saw a Windows Explorer open in my computer; I simply detest that aberration of a file utility. BUT, sine you mention it, I will launch it and play around with it. Will let you know. In the mean time, THANKS again for all your contribution.

Ok. Leo! Followed your suggestion about checking if the previously described PDF behavior extends into Windows Explorer... IT DOESN'T!
I normally open and close PDF via Acrobat Pro XI version 11.0.8 The slow-to-respond behavior of D.O. AFTER closing the PDF is not present in Windows Explorer.
As I mentioned in my previous thread, I just finished installing D.O. Beta 11.5.7 x64; I will see if this new beta changes anything. Thanks as always.
Best regards!