On Max OS X both Leopard and Tiger, I can't get Reader to work Offline

Here's what happens: I go offline and it loads 2000 items in Firefox. This works perfectly as long as the browser remains open. If I close the browser and turn off wifi, bringing up the browser again does not work. It says it can't load the page just as it would for any site when Internet is disconnected. Maybe I am missing a URL? Or does the browser have to remain open?
I have read news on the train for example, but only if I leave the Mac in sleep mode with Firefox open. Otherwise, it will not show the page. On my Tiger Macbook, it shows the page for a quick second, then goes to the message about not being to find it.
I've looked over Googles forums and help but ironicaly, I don't find searching Google very effective.