@Nick2K4
I got my A1200Desktop connected to a multi-sys TV(NTSC/PAL). RCA jack. Very clear. The flickering is quite normal on TV's. They don't have enough Hz to keep up thus causing it to flicker, especially in interlace mode. My little fix is to set the color to a minimum just slightly enough in between black and white and set your WB color a little dark. a thin black line and a totally white background causes that flickering effect.
As for your disk access problem, have you tried to distance the TV away from the amiga? I probably causing to interfear with it when both are close. give it a try.
