Hello, Grahame.
Does uninstalling AVG resolves the issue still? If yes, please uninstall and reinstall AVG once to resolve the issue. Click on this link http://support.avg.com/SupportArticleView?urlname=How-to-troubleshoot-issues-after-upgrade-to-the-latest-AVG-antivirus-product for instructions to download and run AVG Clear tool to remove traces of AVG completely.
Note: Do not select the Uninstall Zen and Framework check box and click Uninstall.
Then refer to steps in this link http://support.avg.com/SupportArticleView?urlname=Download-and-install-AVG-Protection on how to download and install AVG Internet Security - Unlimited.
Followed instructions, uninstalling fixed problem. Reinstalled , same problem , clicked "send & receive" & popup said "a/c cannot connect to server" So its blocking email a/c. Uninstalled AVG again & a/c connects to server. Next step please