Just for info, I’ve just tried the CSS fix and it worked fine. I’m using the suffusion theme and added it via the custom includes. Many thanks!
I’ve just changed the ‘freshness text’ – the files to change are, in fact, loop-forums.php and loop-topics-php.
There is also a plug to do this but currently it won’t change the freshness string, though it says it will. It does change other strings though. It’s bbpress string swap.