Sure, inSSIDer shows those signals, but how many dB are they and how constant are they? Periodically, some signal will arrive at the laptop adapter, but it is not consistent enough to provide much if any real connection. Hence the bars may appear good but you cannot really get a decent connection.
A G adapter has a maximum theoretical speed of 54Mbps, but even right next to the wireless radio it will be significantly less (early Cisco whitepapers estimated 22Mbps total throughput in good to excellent conditions for high quality G radios when B was not used in conjunction).