hardly reproducible bug, but constantly encountered.
when you do a number of searches with more then 300 resulting files (i don't think that 300 is a precise threshold, but it's hard to make a search with, for example, exactly 270 results to test it) you can encounter a situation when file won't be added for downloading by standard means (double-click or context "download"). nothing will happen no matter how many times you try to add it. last time i saw this was quite a long ago, so i don't remember if subsequent searches was workable or not, but very probable not.
the workaround is in adding this file by fast link handler - it works.
