FULL PRODUCT VERSION :
java version "1.8.0_11"
Java(TM) SE Runtime Environment (build 1.8.0_11-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.11-b03, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
OS X 10.9.4

A DESCRIPTION OF THE PROBLEM :
Was originally reported agains JetBrains' java-based products (http://youtrack.jetbrains.com/issue/IDEA-114252)

The same problem has been reported against NetBeans (https://netbeans.org/bugzilla/show_bug.cgi?id=88161)

The problem is that external clipboard managers doesn't work well with java app (java app misses clipboard changed made by the manager until user de-active/activate java app)

It looks like the problem is that current clipboard implementation check if native pasteboard has been changed when app window has been activated only, which is ok for most cases except when external clipboard manager is used (because it doesn't de-active java window).
 

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
To reproduce the problem you can use simple java program attached to the ticket (see http://youtrack.jetbrains.com/issue/IDEA-114252#comment=27-630494)

Run the app, and external clipboard manager (such as ClipMenu or LaunchBar)
copy something to clipboard in native app, copy something in java app, try to paste the first copied text with a clipboard manager

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The text will be pasted and the test java app will print the content in output
ACTUAL -
the last copied text will be pasted and the java app will not detect clipboard changes until the app will be de-activated/activated

REPRODUCIBILITY :
This bug can be reproduced always.