Hello EGHelmut and welcome to the forum,
Since you updated Avast from 5.1.864 to 5.1.889, I suggest that you do an uninstall and clean (fresh) install of Avast 5.1.889 to fix your problem.
1. Save a copy of newest version of Avast
for the product you need and save it to your HDD:
Build
5.1.889 download files:
Free:
http://files.avast.com/iavs5x/setup_av_free.exe2. Download the Avast Uninstall Utility
http://www.avast.com/uninstall-utility and save it to your HDD (it has uninstall tools for all Avast versions and products).
3. Disconnect from the Internet at this time.
4. Go to Control Panel and uninstall Avast through Add/Remove Programs if possible and reboot.
5. If Step 4 fails, boot into
Safe Mode (hit F8 repeatedly) and run the Avast Uninstall Tool.
Uninstall all previous versions you had on this machine at this time.
6.
Reboot.
7. Install the newest version of Avast and
reboot.
8. Get Internet access and register your copy for Free:
Free –
http://www.avast.com/registration-free-antivirus.php9. Update the Avast definitions.
Let us know if this fixes your problems. Thank you.