Fluid apps open new windows in "default" browser rather than the SSB

There are two sites that I use regularly that don't want to play nicely with Fluid. Both of them require signing-in, and both seem to issue some variety of HTTP redirect after authentication. When the Fluid-app gets the redirect, it chooses to open it in a new window for some reason. Since my default browser is Firefox, that ends up opening the page in FF instead of the SSB itself.

I've also noticed something similar when using a SSB configured for Google Reader-- when I click on an article title to jump to the original URL, it "launches" it as though I had clicked a shortcut from the desktop. It ends up in a FF window (or in my case, a new tab in an existing window).