do you finish editing and then go straight into the burn module and then burn the disc - many people including myself had all sorts of little niggles doing that. I now finish editing and then create a DVD compliant file - then I check out that file in Media player or some other player first to check it.
Then I open the Create disc Module and if there is any thing in the timeline I delete it - then use the 'Import Media' option to import the new and checked file - this makes sure I am burning a good file to disc - BUT I do not burn to disc at this stage, I usually use the 'Create DVD Folders' option which makes a Video_TS folder on your computer. Next I use WinDVD to 'play' that Video_TS folder, then if all is well I just copy that folder to a DVD.
Might sound a bit long and convoluted - but it actually is quite quick - but very importantly I get good discs with no problems - and - if there is a problem I can Isolate the stage it occurred at and put it right before I waste a blank DVD.
Of course if you already do that all this doesn't help - in which case - sorry.