JacktheMac, not sure what your issue could be, but you could try renaming the file called "com.apple.iDVD.plist" (just spotlight it to find it) to something like "com.apple.iDVD.temp" and then try to open iDVD again. the app should recreate the plist file. in some cases with some apps this will work, so it's worth a shot and it can't hurt anything. if it works just delete the original file you renamed.
JackBauerPower, to burn a data dvd just create a burn folder anywhere, drag the files to burn to it (this will create aliases/shortcuts to your actual data). then right click on the burn folder and select "burn disc." you will be prompted to insert a disk with enough room. pop in a dvd and you will then be prompted to name he dvd, select your burn speed, and then you're off!
