Shoutbox

Please don't use all bold characters, it isn't needed for anything (and annoying to read).

Anyways, have you tried using Messenger without Messenger Plus!? Simply keep Plus! uninstalled for a while and see if the problem still occurs.

This said, I dont see how Plus! itself can cause your Messenger connection to get lost. This sounds more like a problem with your internet connection itself and/or the Messenger servers.

Though some scripts for Messenger Plus! could cause this (but not very likely), so make sure you also try to disable all scripts.

Also, there are many addons and patches for Messenger, disable and uninstall them too (again not very likely).

And did you tried to re-install Messenger itself? (you are not clear about that as you don't say what you have uninstalled and reinstalled).

So:
1) Disable all scripts in Plus!:
Plus! > Preferences > General > Scripts > untick everything > OK
Then see if the problem still occurs.

2) Uninstall Plus!
Then see if the problem still occurs.

3) Remove, uninstall, disable all the other patches and addons you might have. The best way to do this is to uninstall Messenger completely, redownload it and install it again.
Also check out the Connection Wizard and Troubleshooter in Messenger.
Then see if the problem still occurs.

4) Disable (or properly configure) the Firewalls or other internet security software you might have.
Then see if the problem still occurs.