Mountain Lion System Freeze - Poor Memory Handling?
Since re-install Mountain Lion my system freezing very often (randomly). It seems like disk freeze for 15-30sec. I suspect some bug. But after huge effort to investigate problem I found that in my case the solution is to delete sysem logs.
In terminal:

sudo rm /var/log/*


I don't know what was wrong (it was clean install of ML) but it work for me (two days until now) and looks stable.