Hello i have downloaded musicvideos from youtube but these are in FLV format is there an kde application that can convert to mpeg or avi so i can watch them on mine Black Berry.

so many ways, so many products

kde
kommander tool http://kde-apps.org/content/show.php/FL ... tent=33973
avidemux2 http://fixounet.free.fr/avidemux/ (qt4 actually)
service menu http://kde-look.org/content/show.php/co ... %2Cavi%2C..)+to+?content=66658 there other service menus also
Hyper Video Converter http://kde-apps.org/content/show.php/Hy ... tent=67781

Plus non-kde
web based dl & converter http://clipgrab.de/start_en.html
command line ffmpeg -i old-file.flv new-file.mpg
web based dl & cvt xviservicethief http://xviservicethief.sourceforge.net/
cvt handbrake http://handbrake.fr/

there's lots more out there, some might have presets applicable to your device

Did you mention the raw konsole program 'mencoder'? (however many video-programs are based on this)
And we could go on nearly endless

Try this one:
http://www.miksoft.net/mobileMediaConverter.htm