Invalid file types (upload xls/xlsx)

Sorry for my bad english, because I speak on other language.  

I have a next problem:

1. On two computers installed the same server (denwer) with same versions.
2. I copied all folder with my project and his base from one computer to another.
3. My code contains validation of mime types of uploading files (I use upload library + form validation).

PHP Code:

$config['allowed_types'] = 'txt|csv|xlsx|xls';
$this->upload->initialize($config); 


And it works excellent    , but only on first computer   . On another computer (where I copied my project), it not works also. Namely, .xlsx and .xls files do not pass the validation!    I get message "Invalid file type" !

In mimes.php there are .xlsx and .xls by default

PHP Code:

'xlsx'  =>      array('application/vnd.openxmlformats-officedocument.spreadsheetml.sheet', 'application/zip', 'application/vnd.ms-excel', 'application/msword', 'application/x-zip'),
'xls'   =>      array('application/vnd.ms-excel', 'application/msexcel', 'application/x-msexcel', 'application/x-ms-excel', 'application/x-excel', 'application/x-dos_ms_excel', 'application/xls', 'application/x-xls', 'application/excel', 'application/download', 'application/vnd.ms-office', 'application/msword'), 


I tried upload any xlsx/xls files in other scripts, that don't use Codeigniter, and there files upload success. So I think that webserver is not guilty.

I don't understand what should I do? Please Help!!!!