"Cannot write file"

Hi,

I have this problem for few days now. I was downloading a file and during the download I had the message that I didn't had enough space on my hard drive. So I've done some space by deleting other files, I've rebooted the computer and now when I try to open again the download file Safari says to me this error message (download window): "Cannot write file".
Now there IS space on my hard drive, I tried to repair the permission of my disk but I still have this error.

Any ideas?

Thanks a lot in advance for your help!