This is probably the single most annoying bug in Firefox for me, as I have butterfingers when it comes to typing in URLs. Glad to see it’s been reported and hopefully it’ll be fixed in the fothcoming Firefox 2.
“Firefox is setup to use a Squid proxy server. I attempt to visit a non-existant domain that will bring up a DNS error on the proxy server. The moment between me submiting the address and the proxy server returning the error, Firefox locks up the system. […] It is not until the proxy server returns the error that I am able to continue working normaly.”