OS X Yosemite - Developer Preview 3

[creeper]

Reset PRAM and SMC. Start in single user and run disk utility again. Fix permission.

If single user works fine. Then it might be some software cause the chaos.

But generally. If an Apple freezes, it tends to be hardware related.

 

[Lord Flacko]

Safe Boot the Mac. Hold down shift. If you login without any issues, click the Apple logo -> About this Mac -> System Information. On the left hand side, look for Software and then Installations, compare the dates of which software was installed prior to the issue.