First of all can I ask a couple of questions please?
1. Why donít you use Adobe Encore as the DVD author as it is in with CS3?
2. Why are you going via File> Export, when Prem CS3 has Adobe Media Encoder?
Some of the problem might be if you have a bootleg copy of CS3 Ė I am reliably informed that bootleg copies have certain parts missing that will be downloaded once run for the first time and registered, however im not accusing you of having a bootleg Ė Try this-
New Comp, Pal DV, Import all assets and set them to the timeline in a row (No fancy things as this is just a test)
Once ready go to
File, Media Encoder, Choose a preset for Pal DV (Not Mpeg DVD) and export this to a folder.
Open Encore and import the just rendered file, set it as first play and burn a tester DVD.
I did a small tester last night and found no problems.
Let us know how it goes.