Playing NTSC games at 50hz on PAL console

after playing around with dreamsnes and nesterdc se my dreamcast constantly displays ntsc stuff in pal 60 instead of pal 50. while this would be desirable for most users, for me it's not, since either the pal 60 signal is somehow broken, or my tv just doesn't handle it right, although it supports this mode.

so, before using both emus everything worked fine. i suspect nesterdc as the culprit, but i don't have any clues what could have gone wrong. it was just the last program i used before everything screwed up. pal stuff still runs fine, but not ntsc programs.

is there a way to permanently setting the console to 50hz?
a guy here posted a similar problem a week ago (http://www.dcemu.co.uk/vbulletin/showthread.php?t=60553)
his console always used 50hz for ntsc games, so there has to be a way to set mine to that mode.

i reseted the flash memory just in case something got screwed up. i left the console unused for a month for other memory to clear. i used swats regionchanger 1.5 (but without the hardware mod), but it doesn't offer a 50hz mode, except for the normal pal, which my dc was already set to. the only option as i see it, would be to get dc-x, but i wasn't able to find it anywhere. neither ebay nor international gameshops had it. but still that would only help temporary. does anyone have an idea how to set the video signal to a constant refresh rate?