I was using nicotine+ version 1.2.6 on my debian box and realize that "Free Slot" search filter wasn't work fine.
Then I've tried the lastest version 1.2.7.1 and the problem continued. So, let's take a look at the code :)
Then I've got a problem at search.py, where the nicotine updates the filters (I guess the problem was in translate the value of "Immediate Download" variable to locale...
2007-03-14 03:38:32 UTC in Nicotine-Plus: PyGTK2 Soulseek Client