I don't know why, but spotify clients seem to crash whenever user attempts to change playlist cover, change storage location or anything that makes Spotify open up the system's file browser.
People on Xfce don't have this issue.
Easiest way to avoid the issue is using an older Spotify client. Version 1.1.26 should work ok, you can get it from here.
There is also a new version (since November), 1.1.46, but I don't know if this has fixed the issue either.
Let me know how you get on!