"The filetype you are attempting to upload is not allowed" showing only on server

[eluser]florin[/eluser]
Hi all !
I've got some trouble with file upload class. Everyting works on localhost(xampp), but when ive put it on server shows me "The filetype you are attempting to upload is not allowed".

Can anyone help me ? What could be the problem ? Serverside ?

Ps:i upload pictures