cannot have avast to run!

Hello,
I have win 8.1 and am using avast from the beginning of time
I asked by a right click to scan a downloaded file and got the message that avast ui should be running first. I then noticed that indeed I dont see the avast ‘virus’ logo on my notification area and that it is not listed in the notif area icon lists I then launched avastui.exe from C:\Program Files\AVAST Software\Avast but nothing happened. I then downloaded avast from avast site and launched the installation program. It terminated w/o any notice and I can see the the the avastui.exe had not been replaced: the version is dated Jan 12. All this is very strange.
Any suggestion?
Thanks in advance

Repair Avast:

  1. Control Panel → Add/Remove programs → Avast
  2. Click on ‘Repair’.
  3. Follow instructions.
  4. Reboot.

Thank you!
rebooted (before reading your reply) and all seems to be working correctly again:)

You’re welcome.