Here is how to do it:

Firefox > Options > Options > Advanced [Tab] > Update [Tab]

Then uncheck 'Firefox'. This will do the trick.

Also if you don't want any notifications about updating of other parts uncheck all of the available things there.

If the thing presists, please check here and see if it helps:

https://support.mozilla.com/en-US/questions/867616

If this helped you please hit "Solved it" Button so the topic would be closed.

Thanks for getting back so fast, I'll try unchecking updates.

Am I right in thinking version 6 is still in beta?

If it is now a fully tested version I'll update now which will presumably also solve the problem.

Thanks and regards Ian Tocher

FF6 is latest release and not a beta version.