iceweasel sometimes shows "untitled" when enter url

[yuanwei xu <xuyuanwei@gmail.com>]

Hello,
In this week,after iceweasel is started,it shows "Looking up www.google.com" in the status bar,but it doesn't connect to the home page,just shows "(untitled)".It also happens when I open link in new tab or iceweasel failed to refresh page to the new link I clicked in the current page.
This problem is very often.What may cause it?
Iceweasel version is 3.5.13 on Debian squeeze.