Back to =< Netbeans 6.5.1, when you updated the JDK, and installed the new version, Netbeans wasn’t able to start due to a missing JDK. You could start Netbeans with –javahome
switch to point to the new JDK to avoid a terminal error.
Or you could open the <NetbeansInstallDirectory>\etc\netbeans.conf, and in there you would modify the netbeans_jdkhome var.
As for Netbeans 6.7M2 this is no longer necessary. It searches for another IDE when it can’t find the original one. Though this is just for THAT session. So if you want a permanent change you still have to edit >blah<\etc\netbeans.conf like stated above.
Good luck 
I feel you – I personally had to switch back to 6.5.1 myself because Netbeans 6.7M3 kept locking up. I depend on it too much each day to beta test the new release, as swank as they are.