Är det en Vista? ;)
In vista TCP Window Scaling is enabled by default. If your router does not tolerate this feature, it can cause random DNS and connection errors. This is a common cause of vista limited connection errors.
http://www.tech-recipes.com/rx/1744/vista_tcp_cannot_communicate_primary_dns_server/
Lite brister som kan uppkomma med TCP window scale option och olika orsaker.
http://en.wikipedia.org/wiki/TCP_window_scale_option
Possible side effects
Because many routers and firewalls do not properly implement TCP Window Scaling, it can cause a user's Internet connection to malfunction intermittently for a few minutes, then appear to start working again for no reason. If "diagnose problem" is selected in Vista, an error message will be displayed "cannot communicate with primary DNS server." [1]
There is also an issue if a firewall doesn't support the TCP extensions. [2]
Another problem arises if there are many devices attached to the same router. If every device wants to send or receive 1GB of data in one chunk (using maximum scaling factor) and is connected to the router with a fast (GBit) interface the router has to store this data until he was able to put it onto the slower (WAN)-line. Very often the routers don't have enough main memory to store all this data at the same time (imagine a company with 1000 computers attached to the internet over the same line). When this happens the routers have to throw away packets. For this reason using windows scaling and large TcpWIndowReceiveSize's (>8kBytes) on WAN lines has to be designed with care. To estimate the maximum window size on a given line take
Inte alls säker här, men se om något stämmer för dig?