Same router as yours. When I do install Version 3.0.0.4.276, it works perfect.
So there's something wrong with the new firmware I guess?
It's working well on close distance, but when I go upstairs, the Wi-Fi signal is not as strong as it was before.
I did a factory reset before and after the upgrade.
See the numerous posts made about this. The new wireless driver has a shorter range, you must use the SDK5 build if you want to restore the old range, at the expense of some features such as XBox Optimisation mode and PPPoE HW acceleration.