Happened to me too... but i guess i need to go get the newest ver. That also means that you have to beat it alll over again.
Oh btw, it doesn't send me back to the starting screen. It just crashes wc3...
Same to me, but i fixed it
1- open the editor
2- click the 'custom campaigns' tab
3- Open the RotD campaign
4- find the level after the one where you choose your dragon
5- right click, and select edit map.
6- save the map, it comes up with an error. If it doesnt fix this on its own, search through the triggers and disable the ones that say there is a problem.
7- save the map again.
You might wanna do this for all the levels after this one too. Also, the gold dragon caused the problem for me, so make sure not to pick it, even though its tempting.