Close button sends client to the tray, statically linked Qt for OSX.
See the Changelog for list of features and fixes currently only available in the nightly builds.
If you're using Soulseek client version 156, please be aware that the server it connects to is no longer online, as it was almost completely empty when we decided to shut it down. Try SoulseekQt or Soulseek 157 NS 13e available on our download page to connect to the new server.
If you are using SoulseekQt or 157, it's possible your ISP is blocking access to Soulseek, as the Soulseek server is almost never offline.
If you would like us to try and diagnose your connection problem, see this post.