I think that I solved the problem. The screwdriver that I used to disassemble and assemble the powder measure was magnetic. I think that this transferred just enough magnetism to cause the powder to stick in the measure.
I disassembled, cleaned and reassembled the measure with a non-magnetic driver, and it seems to be working fine. Keep your fingers crossed, or I will be in the market for a new measure.
Thanks again for all the help!