Hi Steve,
what I know about the protocol is: a 50us pulse followed by 24 clock periodes (6Lo+6Hi=24us)next comes a 100us pulse and once more 24 pulses.the final pulse lasts for 60us what makes a total time of 786 microseconds.
the first value(23bits+sign) is referred to mechanical 'zero'...the second value is referred to
a position you set with the 'zero' button.(remotely settable by shorting the data line to ground)

Steve,what is your cycle time ? Less than 0.5us ?
did you use more than one interrupt to capture the burst?
my circuit uses comparators to raise the signals to a 5 volt level,followed by inverters to get signals with
good shape.
any mistake? what secret formula should I add to get some reasonable data in?
Any genious around?
Thanks for reading
Edgar