See. Use% = 100%. That means "No space left!", regardless of your claim that there actually IS space left.

The storage on your device typically is divided into three parts: root filesystem (/), /home/user and /home/user/MyDocs. The first part is used for all the mission critical stuff. The second is used for optified packages and the last for your movies, MP3s and pr0n.

In this case you need to make room on the first part to be able to install more goodies/receive SMS/whatnots since it's used for that. Removing all your pr0n won't fix it since it's stored on another part.