I'm running the risk of getting out of my depth here but happy to come along for the ride.
You could try using file mode in DVD Decrypter and then try and play the folder first. This will give you a clue as to whether all the data is coming across properly and all IFOs VOBs and BUPs are in the right place.
If it plays correctly you could then go through the whole process again with DVD shrink to see if that sorts the problem.
If it doesn't then maybe you could try and re-author the folder manually with DVD Shrink but you may have to lose some extras to fit everything on.
You could also try and burn using something other than Nero. Also, are you using the latest Nero?
Having googled a bit you could experiment with IFOEdit or IFOupdate. Both these apps rearrange the file structures to try and make sure that everything is in the right place and then you could try to burn. I've never used them so can't vouch for their success. There's another couple of freeware apps AnyDVD and DVDFab Decrypter that do the same job as DVD Decrypter and they may not encounter your original problem.
If everything fails I strongly suggest cracking open a cold one, chilling out and watching clouds pass by for a while as life's too short
Hope this gives you some ideas