After program update Avast stopped working

I got a minor program update and after I restarted my computer, it stopped working, I cant turn it on. What’s wrong?

Which is your firewall? Any other security program that could interfere? Previous antivirus (before avast)?
You can test system restore or even booting in Safe Mode and uninstalling avast.

I have online Armor, it asked me waht to do with ashdisp and something else part of Avast, I hit trust and allow. I tried using Microsoft security center to start it up but it said it couldn’t

Sorry, John. I’ve misunderstood. I’ve thought you couldn’t boot. It’s only avast which stopped working.
I suggest an installation from the scratch:

  1. Download the latest version of avast! Uninstall Utility and save it.
  2. Download the latest avast! version and save it.
  3. Uninstall avast from Control Panel (if possible). If, for any reason, you can’t run it, try booting in Safe Mode and doing it from there. Anyway, boot after that.
  4. Use (run) the avast! Uninstall Utility saved on 1. If, for any reason, you can’t run it, try booting in Safe Mode and doing it from there. Anyway, boot after you’ve run it.
  5. Install avast! using the setup saved on 2. It will be good to accept the boot time scanning. Boot.
  6. Check and post the results.

avast may be stoped by virus ,you can repair avast, you also can use some green security software to scan