hey and welcome to the forum. did you get some information when avast crashed?
what information was that?
avast is installing chrome as default when installing it. if you had made a custom installation of avast you could have unchecked the option to install chrome
it seems like the description you are explanation in your post that avast did not update 100% ok i suggest you try a clean installation of avast this usually fix the problem
download and run the uninstall tool from this link
http://www.avast.com/sv-se/uninstall-utility
reboot your system. download and run a fresh copy of the latest avast program.
and that could be found here
http://www.avast.com/sv-se/download-software
did this solve your problem with avast, if not write back and we have to dig deeper into this.
good luck