Regular Expression validator with file upload control (asp.net) does not work in FireFox

Question

I am using Regular Expression validator with file upload (Asp.Net) control in-order to restrict the files uploaded. My regular expression is as follows:

^(([a-zA-Z]:)|(\\{2}\w+)\$?)(\\(\w[\w].*))+(.wmv|.avi|.mpeg|.MPEG|.mp4|.MP4|.flv|.f4v)$

It gives error message of the validator even after uploading the right file in Firefox. But it works fine in IE.

Any one please help me providing a browser compatible way to validate my file upload control.