Great this really bites.... it points to the downstream oxygen sensor... one code says the circuit could be at fault... the other says it's a monitoring error... wtf should i replace it (for $145) or look for some other problem

Time for a new rear O2 sensor. Look at www.oxygensensors.com for a good price and mention maxima.org for a discount.

Get a universal sensor - wire it up yourself and save about $85. An O2 sensor is an O2 sensor - Bosch is a good name (what comes on the car stock, IIRC).

Trav