Perfectly normal. If your router is WiFi certified, channel width drops down to 20MHz whenever there are nearby radios detected.
Ok, so if I set my router 2.4GHz N to (force) 40GHz width in stead of AUTO, my laptops should work. I just might PO my neighbors.
Are there wifi cards that can't do 2.4Hz N 2x2 40GHz width?
What if I have a guest come over but his laptop doesn't have 2x2 N 40GHz width capable wifi? Will the guest laptop not work on my router? or can it still connect at 20GHz width somehow?
They will only see the primary channel and won't channel bond to get 40 MHz. For ex. Channel 1 (P) and 5 (S). Those who don't accept 40 MHz will still connect but only on channel 1. That's the reason N is backwards compatible with G even if the router is configured to N mode only (i.e. 40 MHz).