Ok wait a minute now............are you saying this monitor displays NTSC or PAL hiresinterlaced without you putting it in DblNTSC or DblPAL or Multiscan?
have you tried games? and more importantly, does your workbench flicker in 15khz mode on this monitor? because if it doesnt..either you have your Amiga in DblNTSC or Multiscan (Simple way to know is plug into TV at the same time) or that monitor has an internal Flicker Fixer :-)
Whats the namebrand?