Can't see any block in Minecraft (excepting entities)

When I try to play Minecraft, I can't see any block. I can see entities (dropped items, itemframes, paintings, falling gravel, etc)...

Here's a screen-shot:
http://i61.tinypic.com/2vvvtsl.png

And my video card:
ATI Radeon HD 5400 Series

Please help me!