Install Avast on Ubuntu

I Install Avast on ubuntu: every time I start the avast it ask me for registration key, which I supplied (10X) now and avast is keep on sending me the registration key every time I ask for it. This is window will appear every time I start the Avast.

Avast! Information

Deleted stale lock file ‘/home/efren/.avast/lockfile-efren’.

I have no option but to click the OK button.

Can anyone help sort this problem?

This might be best on the avast 4 Linux\Unix forum, http://forum.avast.com/index.php?board=5.0.

The Linux forum is the right place for this as David mentioned.

Have you run the following commands in a terminal as described in the link below.

cd /usr/lib/avast4workstation/share/avast/desktop

sudo ./install-desktop-entries.sh install

http://www.debianadmin.com/avast-antivirus-for-ubuntu-desktop.html