The filetype you are attempting to upload is not allowed.

[eluser]InsiteFX[/eluser]
Yes that could be your problem, you may need to get tect support to turn it on.

[eluser]EOSullivan[/eluser]
I've had the same issue as earlier posters. Can upload DOC, JPG, PDF but XLS files fail.
I've checked the MIME settings on CPanel and Apache and both seem to be fine.

Any other tips or suggestions?

[eluser]EOSullivan[/eluser]
I moved the code around in the upload.php and the error with XLS files went away .. moving the image check to the end resolves the issue ..
I took the cue from this posting
http://ellislab.com/forums/viewthread/70998/#802688

[eluser]Unknown[/eluser]
i got the seem problem and i try to check upload libraries in "system/libraries/upload.php" go to line 201 you will see variable name "$this->file_type" and force it to show the output of it like this

Code:

die($this->file_type);

that variable show "application/msword" for xls file and "application/x-zip" for xlsx file. so, i'm just put this thing in "application/config/mimes.php" like this

Code:

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

and it's work! that it!