Website gets blocked for multiple users

Hi Bart,
We understand the concern and apologize for the inconvenience caused due to this issue, To check and assist with the issue better please submit the sample of the issue using the below link.
https://secure.avg.com/submit-sample
Thank you.

Since a few weeks ago we get complaints of users of our web application that they can not load the page. They get a ERR_EMPTY_RESPONSE (324) error. We didn't know what caused it until now. Apparently they use Avast or AVG, and when you load the page with those anti virus software packages the page will be blocked.

What could be the reason for this and how can I solve it? I tried to check several blacklists online but every tool says our site is save and not blacklisted.

There are too many users to tell everyone to just whitelist our site. The strange thing is that it came out of nowhere. We never heard of the error before and all of a sudden multiple users have this problem.

Hello Bart,
We apologize for the inconvenience caused.
Could you please suggest users to check with the websites after disabling AVG?
If they are using latest version of AVG, please disable each components of AVG and check if the issue persists.
Thank you.

Hello,

We have one computer where we could reproduce the problem because it runs AVG. When we added the site to the AVG whitelist we could visit the website again. 

The problem is we have a lot of users so we can't contact them all to let them now they should go to multiple steps only to visit our website. The strange thing is that also Avast users have the problem.

Bart, Quote "The strange thing is that also Avast users have the problem"… Although Avast acquired AVG you'll still have to contact Avast separately.
AVG Guru

Hello Bart,
We certainly understand your concern. If you have submitted the sample, we will analyze it and add your website to our white-list if it is a secure link. Unfortunately we couldn't confirm it is an old SSL protocol issue. If there is such issue we will hear back from our technical team.
Thank you.

What could be the reason AVG blocks our website? It is hosted on a Ubuntu 10.04 server. Could that be a problem?

Hello Bart,
We apologize for the inconvenience caused.
Could you please suggest users to check with the websites after disabling AVG?
If they are using latest version of AVG, please disable each components of AVG and check if the issue persists.
Thank you.

I already filled in that form, no reply yet.

Hello Bart,
We understand your concern. If you are developer, please follow the steps in this article http://www.avg.com/us-en/whitelist
Thank you.

I know I can whitelist for AVG but I also have the problem for other firewalls/virus scanners. Is there any way I can figure out why you and others are blocking our website? Could it be because of an old SSL protocol?

But it is also AVG that gives the problem.