Firefox local webapps problem

I'm having problems getting firefox to 'connect' to webapps running under tomcat on my mac. It connects fine to external websites, but I get a 404 if I try to see running webapps under localhost.

Safari runs them fine. E.g. http://localhost/blah/ in safari runs blah, in firefox I get 404 and doing curl from the command line returns the html of the correct page.

I'm not sure if this is a mac, a firefox or even a tomcat problem, but I suspect that it's a setting on my mac that I need to change. I'm reasonably confident that tomcat is ok as http://localhost returns me the apache page to say tomcat is running and installed.