It looks like the client window is way wider than it should be. There's code to try and make sure that doesn't happen when the client starts, but it doesn't seem to be working for some reason. I need your configuration file to try to reproduce the problem on my end. In a terminal, type the following:
cd ~/.SoulseekQt/1
zip ~/Desktop/soulseek-configuration.zip *
There should be a file named soulseek-configuration.zip on your desktop, please mail it to me via private response.