I did read on the OS X section of this forum that other people were having problems with 4.0.5! (I happily use 4.0.4) Even the engineer remarked that version 4.0.5 had a problem. Either try version 4.0.7 or ...
Also on this forum I found this note:
the old free installers for all platforms are stuffed into one large archive (~70mb). http://www9.limewire.com:82/download/ has the 3.8.10 and .11 installers.