The usual ?format=feed that seems to work on most sites is showing a blank page.

A solution asap would be great.

try turning on error reporting and see whats the error message. Another way is to use the default joomla template and see if it's also showing the blank page.

Thanks Kannan!

I always forget about Error reporting. Turns out it was a Fatal Error with 'System - GK Open Graph Article Parameters' Plugin by Gavick. I'll let them know...

Disabled it and everything works a treat! Thank you!