This is very Bad problem.. My spotify has been keeping some songs unplayable for some time now. Sometime it allows me to play them, but sometimes it wont. It keeps doing same thing with different users. When i try to add em to play queue, it just displays "NaN" as a lenght of a Song. No information of the song. Today i reinstalled spotify only to discover it had lost all songs. Nothing on my playlists, hottest playlists or suggested playlists. Also today i discovered that i couldn't access Spotify web player -web page. Internet connection was fine but when i tried to access open.spotify.com or play.spotify.com. Told me that My Internet connection wasnt fine. Other websites and connections worked fine at The same time. www.spotify.com worked good.
I use Windows 8
PS. Your comment section page captha-check sucks.. i had to confirm myself as a person 5 times while writing this on my phone