In the redesigned client (v0.9.8), multiple reports of almost all text being missing.
Desktop v0.9.8 is currently rolling out, if you don't have it yet it will make it out to you sometime in the future.
Open Spotify v0.9.8 on some systems.
The majority of the text in the client will appear to be missing, but the client still operates normally.
Try altering your Windows Color Depth between True Color (16 bit) and True Color (32 bit). (Instructions on how to do so are here).
If you have an nVidia hybrid/optimus graphics system (reported by @octodur ), make sure the Intel Integrated graphics processor is set as the system default in the nVidia Control Panel. Screenshot and extra details here.
Until this issue is resolved, you can also use the web player.