This has happened to me a few times… with a few different WiFi routers, so I suspect its a common flaw.
While setting up wifi accesss, most access points offer options like: B+G mode, B only (up to 11Mbps), G only (up to 54Mbps), and turbo (108Mbps) modes.
To me, it looks like the G-only mode has advantages such as less interference with 802.11b devices, and thus, better speeds and coverage.
I don’t want to support the virtually extinct “B” devices… so flipping the WiFi option to G only, should be an obvious decision, right?
I have found quite a few WiFi routers, when they are switched to G-only mode, will actually switch to B-only mode!
The amount of headache that has generated (for me), means that I now leave the WiFi option to the default B+G mode (or whatever “auto” mode the access point will allow.