Problem with avatar, images, icon, all pictures

Hello, I have a problem: I installed several times elgg 1.7.6, and all went well, I made some users with profile icons. Then, next day, I open my new elgg net and is all well except the profile icons and all pictures uploaded. None of the pictures uploaded appear. When I try to change a profile icon, elgg say that is well uploaded but nothing appear. 

I look some documentation and the troubleshooting page but I cant find nothing.

Thank you all for the help!

excuse me my bad english, but I speak spanish as a mother language ;-)