Getting logged out of forum when visiting arduino.cc

Why is it I sometimes get logged out of the arduino forum when I open a new browser tab to the arduino.cc site?
Many a time I have been in the process of composing a reply to someone on here and just visit the main site to get a URL reference only to find I have been logged out of the forum and my partially composed reply has been lost. :0

Which browser are you using?

[quote author=Coding Badly link=topic=172712.msg1284849#msg1284849 date=1371674550]

Which browser are you using?[/quote]
Firefox v21.0

What I'm using on several computers and I have not once had the problem. I'm going to go with... buggy add-on.

I would assume (maybe wrongly) it's some form of cookie expired problem but AFAIK NoScript & AdBlock don't effect them. I do have 'Accept 3rd-party cookies' turned off and 'Delete all cookies on firefox close' selected. This problem also effects PC at work and home.

It can't be as simple as an expired cookie. I occasionally go weeks without using this computer or my iPad. I have only had login issues the few weeks when the forum was experiencing technical difficulties. I don't think that was a cookie problem.

Also "expired cookie" doesn't fit the symptom very well. The cookie would have to expire between using the first tab and opening the second tab. Something like that may happen once or twice in lifetime.

I do have 'Accept 3rd-party cookies' turned off and 'Delete all cookies on firefox close' selected.

I'm using Firefox as it comes from Mozilla (I don't even know where those settings can be changed). Maybe it's a problem with Firefox.

I can confirm this issue.
Same behavior. Different browser tested (Firefox & Chromium). Linux box.

This problem effects me at work as well as at home. Same browser but different PC & ISP. It's just a bit annoying to spend time composing an answer and then going off to add links to relevant arduino site and find the message deleted. I just give in now and don't bother replying.

How often do each of you access the forum?

Pretty much every day. Sometimes I will stay logged in all day and periodically check for new messages. Other days I will log in and out several times checking messages.

Is a proxy server involved?

[quote author=Coding Badly link=topic=172712.msg1298549#msg1298549 date=1372617526]
Is a proxy server involved?[/quote]
At work a proxy server is involved but not at home. They are both using Firefox with AdBlock & NoScript plugins. They are also set to not accept 3rd party cookies and delete all other cookies when FF closes.