Error uploading PDF

[eluser]shahmy[/eluser]
Hi to all I also get same error for uploading pdf files.
when I try using opera 10 it work properly. but when I use
firefox 3.5 it was getting error. and my mimes.php contain

Code:

'pdf'    =>    array('application/pdf', 'application/x-download'),
'pdf' =>  array('application/pdf', 'application/x-pdf', 'application/x-download'),
'pdf'   =>  array('application/pdf', 'application/x-download', 'application/unknown'),
'pdf'   =>  array('application/pdf', 'application/x-pdf', 'application/x-download','binary/octet-stream', 'application/unknown', 'application/force-download'),

that mean i was try one by one above pdf configurations.
but it getting the same error.
please solve me this problem.
Thank you.