by disabling hbbtv plugin you're speeding up stb, what means more memory is available to deal with image processes. If you'd like to get more space in flash I'd suggest to extend your flash using USB stick as it's written here:
http://www.vuplus-community.net/board/threads/howto-extend-flash-in-bh-images.8187/[/quote]
It is also possible to un-install Hbbtv yourself. Via green panel look for installed plugin's and locate HBBTV which will be signalled as installed (the globe highlighted) and then you may do an uninstall there. The method described via USNB is preferable but obviosuly requires to get familiar with Parallel Universes first. It is worth the effort though.