Steve:
Consider this,,,,A pin being an input will have leakage characteristics. The leakage may or maynot be secified in the microcontroller data sheet. Now consider a powered down device attached to that pin. Its connection which may be an input when the part is powered up may look like a low impedance (often due to input protection networks on that powered down device) when the thing is powered down. This can thus become a sink for the leakage current from the 'LPC932 pin that you made an input. However it could be that if the 'LPC932 places the I/O pin as a LOW output the sink that the external device was offering may be reduced to the point wherein the '932 current attributed to this pin may end being less than the input leakage current from the prior configuration. (Note that I have seen this several times!) Consider also that even though you may be talking a small .05 uA difference you take and multiply that across 20 I/O pins and now you are significantly into the microamp level you are trying to achieve.

Michael Karas