What monitor are you using this time?
A lot of SDTVs (and some monitors) can do modes close to either PAL or NTSC but don't like anything too far away from 50Hz or 60Hz, typically in the 53-57hz range though this varies. If you have a single crt_range in your monitor.ini preset that covers everything between 50 and 60 Hz, VMMaker can automatically generate these middle-muddle-50s modes, and switchres can choose them thinking that your monitor can handle it.
One way around the issue to to just stick with one, either 50 or 60hz, but then you lose a lot of potential.
Another way to get around the issue is using 2 crtrange presets in the monitor.ini - one crtrange for NTSC or 60Hz-ish modes, another crtrange for PAL or 50Hz-ish modes.
For example, here is a preset I setup earlier for my Chinese component-modded TV (though in this case I don't actually need to block out the mid-50s modes):
monitor "ChinaTV1", "China TV - 50/60 Hz", "4:3"
crt_range0 15625.00-15734.26, 49.50-55.00, 1.500, 4.700, 5.800, 0.191, 0.191, 1.056, 0, 0, 192, 288, 448, 576
crt_range1 15625.00-15734.26, 55.01-62.00, 1.500, 4.700, 4.700, 0.191, 0.191, 1.056, 0, 0, 192, 240, 448, 480
The numbers in italics are the vertical frequency ranges (you can tweak to suit your display), and the numbers in bold are maximum vertical lines. Grooymame will now choose from crt_range1 for modes up to 240 lines, and from crt_range0 for modes with up to 288 lines.