@Gazelle
Cheers for the advice! Ive just checked the technical data sheet from Dell for my 1505FP 15" TFT monitor, and it shows that the polarity for the 800x600 are both plus for the hsync and vsync yet they are both negative for 1024x768
Could this be it? Maybe OS4 defaults to plus plus for all resolutions maybe?
Gunna try it when I get home and let you know the results
Heres a link to the technical datasheet
http://support.dell.com/support/edocs/monitors/1505FP/EN/about.htm