@
atulk,
You should not run 2 (or more) antivirus programs on your machine at the same time as they often create conflicts. I suggest that you uninstall both Avira and MSE, even if you have done so already, since remnants often remain. See the links below for uninstalling…then reboot your machine after each uninstall.
Avira Uninstall:
https://www.avira.com/en/support-for-home-knowledgebase-detail/kbid/88http://www.themisteriosos.com/uninstall-avira-antivir-completely.htmMSE Uninstall:
http://support.microsoft.com/kb/2435760http://support.microsoft.com/kb/2483120 / - if unable to uninstall from the above link
After uninstalling the above and doing the reboots, see if Avast works properly. If not, it may have been corrupted by the other AV’s you had on your system, in which case you need to uninstall Avast with the Avast Uninstaller Tool
http://www.avast.com/uninstall-utility, then reinstall Avast and reboot.
Why NOT to use Revo: Revo and some of the other Un-installers are generic uninstallers. Simply put, they get rid of most of the stuff, but not when it comes to security software.
When it comes to removing an antivirus program, which runs as a service on your system and is in some ways involved in all parts of the operating system, you need a specific uninstaller capable of removing every part of the antivirus program. Without this capability, some critical parts could remain and interfere with the new antivirus program being installed (also called a conflict).
Let us know how this works for you. Thank you.