EDIT: Off topic, but the Framemeister pisses me off with the amount of visual noise the scaler causes in some (actually, many) solid colors.
Would you mind expanding on this a bit? I haven't had mine for very long and I've noticed odd artifacts/something in some cases. Off the top of my head, the solid green background in Dracula X has weird vertical bars going through it. Is that the type of thing you've noticed? I was wondering if there was any way to get rid of such annoyances...
It sounds like you are experiencing jailbars, which is common on rgb modded pce systems. Do a search for pce jailbar fix, it may not eliminate it but it certainly helps.
What he was talking about is certain solid colors will have noise in it. You can adjust the settings, but it may just shift which color displays the noise. On my setup you see it really badly on NES Punch Out.