Starting from jre 1.6u10, browser integration uses a so-called "next-generation plugin".
Some old applications are not compatible with it, and (on windows) it could be disabled in control panel, java, Advanced, Java Plug-in, remove the check from "Enable the next-generation Java Plug-in (requires browser restart)".
The problem is that sometimes this check is grayed out, and it is not uncheckable even if you have amdinistrative priviledges and run as administrator.
Any workaround to solve this?
UPDATE:
I've done some testing on some machines with different operating systems, browsers and java versions.
Initially I've supposed that the problem was w 7 or the fact that it was a 64 bit o.s., but there is a case (case 3) that denies this assumption.
So there is something "else" on a machine that determines this option to be grayed out.
Test O.S Browser JRE version State
1 W 7 64 (Home) IE 9 7u2 64 grayed out
2 W 7 64 (Bus) IE 8 6u27 64 grayed out
3 W 7 64 (Bus) IE 9 6u22 64 NOT grayed out
While looking for exactly the same thing I found a forum post with another clue, more strangeness:
This does successfully remove the tick from the Plug-in box, but the next time the Java Control Panel is opened, it reverts back to "ticked".
The original forum post is here: http://www.sevenforums.com/software/208418-removed-java-add-still-ie9.html#post1754583
A first, simple, not extensively tested answser is:
On 64 bit machines, 64 bit JVMs have that flag grayed out (tested various releases >6.10 and <=7.2) Installing 32 bit jvm, that flag will be not grayed out.
It is obvious that this solution is sub-optimal, but may be a (perhaps the only) solution for some compatibility issues.
You can also click the "add" button, and voila! you can now un-check BOTH boxes for Java and the "new" blank added item.