yes, I have a scandy scandoubler, and those vertical lines are displayed.
If you have a scandoubler I think that it's normal.
Some LCD monitors can display 15Khz vertically through VGA (like ACER K242HYL, which is cheap, but the display isn't perfect). There are others mentionned in this forum. Like that one (not tested personally): Dell U2412M:
http://eab.abime.net/showthread.php?t=85693