Hi cloud,
to install the version 4.5.36 pls read this thread:
http://forum.avast.com/index.php?board=2;action=display;threadid=9007

I’m not sure if 4.5.36 is officially released now, so pls check Your version before doing that.

A beta version is a software not oficially released yet, which is published for testing. Usually such a version may have some minor bugs, which are then corrected during the beta test phase till the software is officially released. Avast beta version are very stable - I have this version installed and had no problems with it.

Are You sure everything freezes - may be the file is a huge archive, which take some time to scan. I assume this file is in one of the temporary directories.

br
Peter