I was getting that for a while then it at least *mostly* cleared up and I can play maybe 20 to 30 minutes without either a network close or a crash. But they both still happen. :/ I'm sorry its happening to you. Your connection speed is okay right? Part of my problem was I was using a very bad network adapter, so I switched to playing on my other computer and ordered a new adapter, it should be here soon.
If you're not sure, go
here and click on one of the locations to test your computer's download speed. My other computer rates at only 200 or so kb (that's REALLY bad) and this computer is over 1,000. But the network speed might only affect network closes and not actual browser crashes. Its just that both those problems cleared up for me when I increased my network speed. So its all I can suggest.