thanks for replying, I am actually setting a pixel clock between 49 and 50mhz.
My monitor needs 49.50mhz to display 800x600/75hz and I tried the 2 closest values on the tool (can't remember them atm I am not near the amiga atm) , the one that is under 49.50 gives a 74hz screen and the one above 49.50 gives a 75.222hz screen.
It feels strange that .222 hz can cause problems whereas a full 1hz lower is fine
Hope this is of help , I am getting a red flashing vertical line on the center of the screen and nowhere else, I can post a pic if you need or provide more details if you think that this could be a bug or wrong setting .
edit: some more info on the artifacts that I forgot to write, I hope they are of some help
They are actually red/pink moving pixels in the center of the screen. They don't always show up. On my normal workbench screen you can see them but if for example you open a full-screen guide file (that has that light gray background) they disappear. Closing the guide makes them show again. They are present on both PAL modes (normal and interlaced) and I have only seen them on the 75.222hz 800x600 screen. 1280x1024 and 1024x768 75hz screens don't have them.