The HTML Help components in Windows may be broken in some way, or something to do with the underlying HTML components they are based on (Internet Explorer, more or less).
I search in the F1 help window quite a lot and have never ran into problems with it, but there are various things that can go wrong with the Windows components it uses.
Reregistering the help components as per here might be worth a try.
If you still get freezes, please generate a crash dump when they happen and send it to us. We might be able to tell why it is freezing, and if it involves any third party components (e.g. antivirus, firewall, or text-input/dictation tools can get involved with HTML components).