Clean install of Win 7x86 SP1 and Avast! installs and works properly. Updated to IE10 and still working. Now downloading updates.
This kind of exonerates IE10, but the install order may be important.
SOLVED: If IE10 is installed on the system before Avast! 8.0.1497 it will hang iexplore.exe *32 and it hangs on the Script Shield and Behavior Shield (if these are disabled or not installed Avast! does not hang the iexplore.exe *32 process). Rolling back IE to the previous version, installing Avast! THEN upgrading to IE10 works fine. This can be replicated in both 32-bit and 64-bit versions of Windows 7 Home Premium.
If a moderator would like to verify this and modify the thread title accordingly, it may help others.