What version of the printer driver are you using?
To find out, use Start -> Printers and Faxes -> Highlight your printer and Right Click -> Properties -> Print Test Page.
The latest USB and GDI drivers for Samsung ML-1510 appear to be ver 1.03; the latest SM driver appears to be ver 1.0.
If you are not up to date then I would start by downloading the latest driver from the Samsung download page
here.
RC