@kregora: Yes, what you describe seems do be exactly my problem.
To your questions, of coure my wife is streamng while I'm playing, but we have 100mbps download and 10mbps Upload speed... I guess the download/upload rates shouldn't be a problem and have it has never been a problem the whole year before.
I also performed serveral speedtests to see if there is something wrong with the performance of my connection, but the rates seem to be pretty steady.
And there is no one else connected to my Router who is playing BF or any other EA game.
There is one thing mentioned in the connectivity guides which I couldn't do. It is the stuff about giving ports free on my router. My router is provided by may internet provider and it does not allow me to do this. Could this cause these problemes? And if yes, why did it work the whole year before.
Anyway I will now have a try and hope that repairing the game maybe fixed the problem. I'll give feedback.
