Since the release of Firefox 6 on August 16th, 2011 the support team received so far 9 incidents, reporting compatibility issues between java console and Firefox 6.
Operating systems reported in the incidents: Windows 7 and Windows XP SP3
Java versions reported in the incidents: Java 7, 6u26, 6u24 and 6u15
Attachments provided by a user: "Screenshot1.jpg and Screenshot2.jpg" were sent by one and same user who reported Firefox 6 regression with both Java 7 and java 6u26
Users reported that they were having regression problems immediately after upgrading to Firefox version 6.
I was successful in reproducing this myself.
Below are my steps to reproduce this issue:
My operating system: Windows 7 64bit
Browser upgraded from Firefox version 4 to Firefox version 6
1. Download and install Firefox version 6 from www.firefox.com
2. Upon completion, the Firefox page relaunches and tells you: "Incompatible Add-Ons"
Attachment: I captured "Screenshot3.jpg" during my installation
In addition, this issue was reported in various forums, here are some samples: