Sometimes have the same problem and have found that rebooting the router cures it.
My setup sounds similar to yours and is to go to 192.168.0.1 - if your password is already saved make sure, at this point, you have a hard copy of it to hand- go to diagnostics and then click on re-boot.
May help
Pleeese, make sure you know your p/word or you'll be really scuppered when it reboots and then asks you for it.
