Why can I no longer get an internet connection when using my old Macbook and AirPort Express? Up until recently I was using my 2007 MacBook perfectly fine with my old AirPort Express. A few days ago I purchased a used mid-2010 iMac which is now running OS X 10.8.3 (something I'm still not too sure I like). When I first brought the iMac home and connected to my network it did so just fine but the AirPort icon in the menu bar showed there was no internet connection, despite the signal being full. I then followed some step-by-step setup which rebooted the AirPort Express and all of a sudden I had internet! Great! …except since then my MacBook has the same problem my iMad had, i.e., it connects to the network just fine but the network icon shows no internet connection :(

I should mention that my MacBook is running OS X 10.6.8. I'm wondering if this is an OS compatibility issue or… Has anyone experienced something similar?
Setting the AirPort Express b/g to g-only mode solved this problem for me, though I don't understand why.