I just saw this in a other thread.

snip: "BT & WLAN on nxx0 share the same antenna as well as same RF amplifier."

Might be also helped by BT on... Maybe some routers don't like this "switching"...

I'll had the problem a few day's ago and it went away by both disabling BT and set for that connection the power saving to "off" (connectivity settings - connections - choose connection - edit last page "advanced" button - 3the tab" )