STEPS TO REPRODUCE:
1) Install jre7 on windows machine
2) Open Java control panel --> Advanced tab
3) Under Java Plugin, by default "Enable next Generation Java plugin" will be unchecked (which is a defect)
4) Try to check this check box

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
By default the check box should have been chaned.
When tried to enable new plugin by checking the checkbox (keeping no browser instance running in the machine), it should have gives a proper message saying, new plugin will be enabled after borwser restart.

ACTUAL -
one message dialog pops up saying, "Java plugin option can not be changed as one or more browsers are running" !!! Even though you do not have any browser instance running in your machine.

(Check the attachment for this exact message, which gets pops up)

And the user finds helpless to enable new plugin !!


PLATFORM:
Windows XP Professional
Version 5.1
(not tested yet on Unix)

JAVA VERSION:
java version "1.7.0-ea"
Java(TM) SE Runtime Environment (build 1.7.0-ea-b76)
Java HotSpot(TM) Client VM (build 17.0-b05, mixed mode, sharing)

ALso tested with java 1.7.0 b199 (PIT build) and this bug is reproducible as well.


IS REALLY OLD PLUGIN UNDER ACTION ?
Though user finds, its not possible to enable to new plugin, but the actual fact is, browsers (FF/IE) are registered with new plugin! To verify that run the below testcase

TESTCASE TO TEST WHICH PLUGIN ?
http://sqindia.india.sun.com/disk17/deployment/subrata/adhoc/testcode/manual/html/PluginTester.html

REPRODUCIBILITY :
This bug can be reproduced always.