When I'm playing this always happen to me.

http://imageshack.us/photo/my-images/842/69770182.png/

This happens when you spawn in a block.
Use your grenades to kill yourself.

Did someone block you? Like put your head in blocks? Well try crouching (Ctrl) or try suiciding.

Soulutions:
Crouch
Kill yourself by either switching weapons, teams, or using a grenade.

^Don't, just switch your weapon and then switch it back before you spawn.

Ben should consider implementing comanche-like raymarching technique, it would get rid of this problem because it simply wouldn't render just the very voxel the camera is stuck in and everything under is just black, so you know where you are and what to do. Also it is very fast on terrains, I'd even bet it would increase FPS. Well depending on the machine though. But then one could simply change it back.