Problem connecting on self (curl, www... )

[blitzmedia]

Hi there

Since a few weeks, 2 or 3, I started having a very strange issue.

The server cannot communicate on self (like doing a curl on it's own ip, or access an image from an url hosted on the same server).

I have 3 servers with the same os, same config, and only this one has the trouble.

Let's take an example of a php website that generates PDF, where in the pdf you have an image loaded by an https:// link that resolves to the same server, the image wont work (because the pdf library makes a curl to the destination to download the image). Or if I try to telnet on port 21 (or any other port) on a domain that is on the same server, it wont connect. (This is a cpanel environnement)

The only way I can temporarily fix it, is to disable the firewall, and restart it.

If I just "restard the firewall", it works back, but only for 1 or 2 seconds.

I have to fully disable it, then reenable it, for it to work for the day. I don't even know when it starts "breaking" again.

Want something strange? If I disable the firewall, it works for a second, then blocks again. I have to reneable it for it to fix for the day.
Sometimes, it doesnt fix, I have to do it 2-3 times in a row, then it works.

This is a complete non-sense, I know.

When its in a "broken" phase, everything works. Emails, ftp, apache, cron jobs, everything works. I can also curl from another server to this server without a single problem, its only from "itself" to "itself".

Ive monitored the logs trying to find when it blocks, I see nothing.
All possible IPS are whitelisted.
Running the latest version..

I dont know where else to find!