I use FF5 as well. I'm sure I've seen that setting but I can't find it now.
I know that if FF crashes, or if we force a close down from the Task Manager, Firefox will re-open with all tabs and windows that were previously opened. But other than setting up 'multiple home pages', I am not sure anything else would work.
Ahh, just found it! General tab, "Startup", "When Firefox starts Show my windows and tabs from the last time".
Try a test. Under the Privacy tab remove the tick for "Clear history when Firefox closes".
I'm thinking that, without History, and without "Multiple Home Pages", Firefox cannot recall other tabs and windows except the home pages already defined.
I have FF 5.0 and I have an issue.
When I have it set to remember my windows and tabs from last time, it
brings up only one website, even if I use the file and exit option.
Private browsing is disabled on my custom history settings, as is the clear history when FF exits option.