recognising certain mime types

I have a new mime type that I am working with and when I click on a file with that extension I do not receive the option to 'open' the file. My only options are 'save' and 'cancel'. I also do not have access to the check box that allows me to tell firefox to use the default application to handle this type. I would either like to setup an application to handle this type within firefox or get the download box to work correctly. Any help would be appreciated.

Kirk