Bike computer

[Owlie]

I rode my bike for the first time in about five months the other day and the computer wasn't clocking miles. The magnet was tracking right and the screen had a readout of total miles, time of day and all that, but it wasn't tracking the ride I was doing.

Any suggestions/advice/ideas about why this would be happening?

Are you sure the magnet and sensor were placed correctly? Mine can sometimes wiggle a fair bit and it takes some trial and error to get them back into alignment. Was the computer reading speed?
Other possibilities:
-Your sensor and/or your computer need new batteries.
-Were you riding near power lines or sensor-activated traffic lights? Both of these screw with my computer. Power lines give me 0. The traffic lights give me a reading of 75mph!