There is a Quicktime reinstaller which will revert 7.1.3 to 7.0.1, which you can then upgrade back to 7.1.2 (I actually did this after I got rid of iTunes 7) but there's a catch - you have a Macbook.
It seems Intel-based Macs can't swallow Quicktime 7.0.1, so it looks like the only way is to reinstall the OS and you will be back to whatever QT version shipped with your machine.