Burning DVD in PAL

I have the following problem:

I would like to burn my DVDs in PAL format but whenever I try to burn I receive the following message 'Trying to burn a NTSC movie on a PAL disk'. If I continue then a low quality NTSC DVD is created. I have tried deleting all media and re-creating the project from scratch. I have deleted and re-installed iDVD6. All to no avail.

I have previously burned DVDs in PAL and I do not think I have changed any settings.

What do I need to do to convince iDVD to burn a PAL DVD?

System set-up:

MacBook
OS 10.4.11
iMovie 6
iDVD6

Project is using a iDVD 5 theme

Settings:

In iDVD6 there seems to be two menus where the media format can be set:
1. Project info -> Video mode
2. iDVD preferences -> Projects -> Video mode

Both are set to PAL

iMovie 6 was used to create the content and there does not seem to be an option to set the video mode