I have the same problems here:
Host-OS: Windows 7 Ultimate 64-Bit
Guest OS: same
My system hangs and (nearly) nothing can be clicked. But I can start the task manager with context-menu on taskbar and for the time the system hangs no applications nor processes are shown. At the time I can work again the task manager is filled correctly. I use only SATA-Controller in my VM configuration so the problem with ICH9 cannot be mine. It's really annoying, simply not usable.
I tried to reinstall Virtualbox and the guest additions in my machine (safe-mode and normal) multiple times but nothing works.
The situation occurs since version 4.1.2. I was lucky to see the update to 4.1.4 but it doesn't help. Before I never had any problems with virtualbox. My host system has been installed new shortly before 4.1.2 arrived. With 4.1.0 it works like a charm.
In my VM no failures were logged, all seems ok. I don't know what to do. Since weeks I am searching for a solution.
I hope there is a solution for me or a few tips from other users what I can try

Kindly regards
tresi