Originally I had problems because I installed version 5 over version 4.8. Had about 5 system restarts when the Help Menu was accessed or the Behavior Shields screen was showing in the GUI. The only work around was holding in the power button about 5 times!
The problem was solved with a complete uninstall of 5.0 through Control Panel/Add Remove Programs. Than I reinstalled version 5.0.377 with no problems. The latest build came out 5.0.396? or 4, not sure of the last number. Only this time I closed out of everything, created a System Restore Point, Disabled ALL running Shields through right-clicking on the Avast Ball. Answered "Yes" to the prompt about the computer being unprotected and that I was aware of it.
Than I did the program update to the latest build, but I said no to the program restart requirement. Waited 30 seconds, shut down through the Start Menu instead, following reboot it's working perfectly as if no problems ever happened before.
MAIN THINGS: 1.) Don't install 5.0 over 4.8. and 2.) Close all Windows and right-click Avast Ball and Disable all Shields when updating Avast Program. (OK to just close Windows but leave Avast running for just manual Virus Definition Updates.)
I would also say:
1.) Shut down all Windows and Version 4.8.
2.) Uninstall through Add/Remove Programs.
3.) Get fresh download of 5.0
4.) Create a System Restore Point
5.) Install 5.0
6.) Reboot will be required.
7.) After about 30 seconds to 1 minute, your AV definitions will update.
8.) Open Avast, click Maintenance and Click Register.
9.) Fill out the form to get new license key and submit.
10.) Under the BASIC settings uncheck the Use Special graphic interface screens
11.) Under connections, DO NOT check "I only connect using a dial up modem even if you have a dial up modem." There are reports that when this is checked it is stopping updates.
12.) However, DO check the prompt "My Computer is Permanently Connected to the Internet" if this setting applies to you.
Jack