If you delete the cookies and it works once and then reverts back to the problematic way then it is something to do with the security settings on YOUR computer. If it was happening to everyone all the time then we could do something about it but experience tells us that most people with a cookie problem have at some time in the past fiddled with their security settings and that is the root cause of 99% of cookie problems.
Don't ask what the solution is if you are not an Apple Mac user as whatever Bill Gates has decided will go on under the hood of your PC is something that is root cause of all evil on earth. If someone with better experience of anything Microsoft and an abomination called Windoze and it's underlying infrastructure of MS-DOS
can explain to the herding masses that are unfortunately brainwashed into the Windoze PC environment of what they can do to alleviate their problems then please do so here.
I regularly check PPRuNe in different browsers and operating systems. Those people who have reported a problem need to check their PC settings. I can only check using the default settings of the bog standard browsers.
Please make sure you have more than one default browser. They are free and if you are solely relying on the Microsh!te offering then do yourselves and everyone else a favour and at least download Firefox or another free browser and see if the problem occurs with those browsers too.