From your description I would guess at a sequence of events like this:

1. Firefox tries to find perlmonks.org and kicks open the network connection dialog.
2. Network connection dialog blocks Firefox's attempt to resolve perlmonks.org until it is dismissed.
3. Network connection is established outside of the Firefox/network connection dialog
4. Canceling the connection dialog returns a failed status on the attempt to resolve perlmonks.org
5. Firefox thinking it can't find perlmonks.org begins searching for similar names by prepending 'www.' or appending '.com', '.org', '.net', etc.
6. Firefox finds www.perlmonks.org since there is now a valid network connection (but fails to update the URL in the location bar?)

I would think 6 (and possibly 4) could be considered Firefox bugs and should be reported.