('os.name') == 'Mac OS X'
('os.version') == '10.9.5'
('os.arch') == 'x86_64'
('java.version') == '1.6.0_65'
('java.vendor') == 'Apple Inc.'
('sun.arch.data.model') == '64'
I created a new world in Creative Mode. Upon finding a temple, I noticed that the pressure plate didn't trigger the TNT. This happened in Creative and Survival modes.
Returning to the surface, I tested all four pressure plate types and found that none of them made the distinctive trigger sound when stepped on.
Then I exited the world and reloaded it, and the pressure plates worked normally.