When I open Avast, the main screen shows my virus definitions version is 110905-0 in red. I click on update button, it seems to connect to server but reports back it’s already up-to-date with 110905-1. Click OK again and main screen still shows version as 110905-0 in red.
How do I correct this please?
try avast repair and reboot
For a repair of avast. Windows, Add Remove programs, select ‘avast! Anti-Virus,’ click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.
did it work ?
Tried Repair but problem still exists.
Forgot to reboot afterwards, as you suggested. Now rebooted and all is OK. Thanks.
Just one more thing. After the repair, I got a Windows box saying something about did it uninstall correctly or incorrectly. i just pressed cancel.
Did you run a cleaner like CCleaner after you uninstalled any previous av you have ever had on your machine? 
My pc came preinstalled with McAfee, which I removed via Programs and Features and then ran McAfee removal tool. I did run CCleaner afterwards.
Since carrying out the repair and rebooting my pc, Avast is now showing the correct definitions version.
you now may edit your first post and add SOLVED to the topic headline