Q: What is denormalization?
A: In short, when the sound doesn’t play, the plugin starts to use several times more CPU power. It’s related with processing of very small numbers very very close to zero (less than -600 dBFS).
Q: Molot 0.3 didn’t have such problems, so why they were added to version 0.3.1?
A: This bug is related with combination of new limiter code and auto-off feature.
Q: What is auto-off feature?
A: When there’s no input signal, the signal processing code is bypassed. If it happens, version string on GUI becomes gray.
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Windows version is updated under the same download link:
http://dl.dropbox.com/u/18475891/Molot031.zip
EDIT: Mac version is updated too (and also support for Mac OS X 10.5 restored):
http://dl.dropbox.com/u/18475891/Molot031.dmg
PS. Reaper performance meter is a good tool to detect such problems!

And also thanks to Theo Niessink! EDIT: And Marc Abram too.
PPS. Also I found the same problem in Proximity plugin. Update shall come soon!