Close FW down, delete the FW preferences folder but save these two files: downloads.dat and library.dat and possibly this third one frostwire.props.
Start FW up again, go through any set up stages, then see if it connects. It may take several minutes to connect. IF it connects ok, close FW. Then replace the new downloads.dat file in preference folder with the old one & any others you chose to backup.

I just tried out File_Girl's FW 4.21.7 Portable & it worked well. http://www.gnutellaforums.com/frostw...frostwire.html