"Invalid UUID" error when saving a Work item after adding a subscriber using firefox ESR 17

Hi All

I am trying to save a work item after adding a subscriber to the work item.  I get a error like this:

"Invalid UUID [https://xxxxx.in.yyyyy.com:9444/jazz/web/projects/_CfuBEEjMEd-5lru_P7rliQ]. "

and the work item does not save.  This has stared occurring since FireFox ESR 17 was rolled out across all of the company desktop and laptop computers.

We are running RTC Version 3.0.1.1

Are there any known workarounds or fixes to this bug ?

(We have 100's of users and dozens of project areas on the server in a full CLM configuration so upgrading the server is a huge exercise)

Thanks in advance

Rob