Error message on log-on

Hello David,
I'm sorry for any inconvenience caused. Please share a screenshot (http://support.avg.com/SupportArticleView?urlname=How-to-create-a-screenshot) of the error message to assist you further. You can post the screenshot here on your topic. Click on 'Answer' & then click on the 'Image' [mountain symbol] & follow the instructions.
Best regards,
Alok.

I reinstalled my free copy of AVG recently, and since then I have had an error message every time I log on:  AVG Diagnostics.  Following AVG processes failed: avgui.exe.  
I have tried a repairing the instal, and also completely uninstalled and reinstalled the program but it keeps coming back.  What can I do to get rid of it?

Thank you for providing the screenshot. This error message occurs when the older version of AVG did not uninstall properly. Please click on this link http://support.avg.com/SupportArticleView?urlname=How-to-troubleshoot-issues-after-upgrade-to-the-latest-AVG-antivirus-product for the steps to uninstall AVG. You can install latest version of AVG AntiVirus free from this link http://support.avg.com/SupportArticleView?urlname=Download-and-install-AVG-AntiVirus-Free.

Hello David,
I'm sorry for any inconvenience caused. Please share a screenshot (http://support.avg.com/SupportArticleView?urlname=How-to-create-a-screenshot) of the error message to assist you further. You can post the screenshot here on your topic. Click on 'Answer' & then click on the 'Image' [mountain symbol] & follow the instructions.
Best regards,
Alok.

Thank you for your reply Karthikeyan.  The error message did not come up again when I logged on today, so maybe it has updated itself.  But if it does come back I shall certainly try your remedies above. 
Best wishes, 
David

AVG error message
Thanks for your reply Alok - here is the error message