TimThumb with wpmu

I am using Micah Theme from mintthemes.com on this site - http://westbrook.missionwebs.org/

The slider and images are not displaying.

It show this error..

A TimThumb error has occured

The following error(s) occured:

Could not find the internal image you specified.
Query String : src=http://westbrook.missionwebs.org/files/2013/01/banner_lifekeys4.jpg&h=392&w=940&zc=1

Please let me know if timthumb it requires any kind of extra settings to make timthumb work with multisite.