If you've enabled Browser Integration, make sure you've got the latest html
templates and history.js.
Thanks for your response.
I tried with the latest history.js and the associated files generated by my Flex Builder 3, but no luck still the same problem.
Is there perhaps a newer version of the history.js, et al that I might be able to try with.
Replacing the HTML template files with the latest copy from Flash Builder 4.5 seemed to resolve the issue. It appears they have replaced the AC_OETags.js with swfobject.js
Tried to explore upgrading the code to 4.5 but seemed to throw a lot of incompatibilities, created a test/dummy project instead in 4.5 and used the html file created to replace the old html files created by Flex Builder 3.0
Clearly not a very common problem, but hope this saves someone time and effort.