With some hosting companies you must not CHMOD more than 755 because of suexec.
Try it!
i change chmode to 755 and i give another error:
The file upload failed. Please choose a valid file and try again. Error details: There was a problem moving the uploaded file to its destination.
the upload folder seems like to crash. Create new folder with the same name. and move the file to the new folder.
no.
same error again
The file upload failed. Please choose a valid file and try again. Error details: The attachment could not be found on the server.
755 will never work, only 757, 775 or 777.
What did your host say about the temporary folder...??