CORS: Firefox does not send POST Request after suc

This works with Chrome and IE, but not Firefox(26).

The OPTIONS request returns status 200, but still Firefox does not send the follow-up POST request like Chrome and IE do.

Request Headers
OPTIONS ..
Access-Control-Request-Headers: content-type
Access-Control-Request-Method: POST

Response Headers
Security
Access-Control-Allow-Credentials:true
Access-Control-Allow-Headers:X-File-Upload content-type
Access-Control-Allow-Methods:POST OPTIONS
Access-Control-Allow-Origin:*

Both IE and Chrome send the follow-up POST method and everything works fine, but Firefox does not send the POST request. I know this because (a) I checked the net traffic in the Firefox debugger and (b) the server does not get the POST request.

Not sure this is relevant but here's some additional info:
X-File-Upload is a custom header needed for a commercial jQuery file upload package I am using
I am using jQuery ajax to make the POST requests

Is this a Firefox bug or am I doing something wrong? How do I even go about debugging this??

Any help or insights greatly appreciated. Thanks in advance.

The list of allowed headers / methods / ... have to be separated by commas, not by whitespace:

Access-Control-Allow-Headers: X-File-Upload, content-type
Access-Control-Allow-Methods: POST, OPTIONS

Although probably not problematic for your current use case, you should also look at the following two headers:

Access-Control-Allow-Credentials:true
Access-Control-Allow-Origin:*

Either remove Access-Control-Allow-Credentials: true, or set a non-wildcard Access-Control-Allow-Origin response header (e.g. http://example.com), because you cannot share credentials when a wildcard origin is used. ^{"The string "*" cannot be used for a resource that supports credentials."}