Sorry if this has been covered, but after a lot of messing about I thought I'd post my info.

After Authoring a DVD and burning it 'region free' I found that it worked great on most DVD players - but not my PS2
Anyway, just for interest I re-burned the DVD after setting the the region code to '245' (Region 2 and Region 4 enabled only) This worked great on my PS2.

I set the region code using IfoEdit to open the VIDEO_TS.IFO file. Click the 'region free' option and you will jump to the correct position in the IFO, right click and 'edit' the value. 245 works for my PAL PS2, check a VIDEO_TS.IFO file on your own region DVD to find the value to use for your area.