Why does my Firefox lose its ability to do DNS lookups?

October 26, 2007 1:32 PM

Every once in a while (time between failures ranges from 1 hour to a few days), Firefox on my laptop suddenly and permanently (until reboot) loses its ability to do DNS lookups. Every page comes up with "Firefox can't find the server at www.foo.com." Other apps (and computers on the network) continue to work fine. It seems random; I haven't been able to correlate it with anything else on the machine. Closing and restarting Firefox doesn't restore its DNS lookup ability, but rebooting does. Googling only turned up the advice to disable IPv6, which didn't help. I'm currently running Firefox 2.0.0.8 on a Dell Inspiron 8600 running XP Home, but it's been an issue since at least 1.5. My only extension is Better Gmail, and I've tried disabling all extensions in the past. I'm at my wit's end - do any geniuses here have a clue?
posted by dfan to Computers & Internet (13 answers total)

Is it only Firefox that can't do DNS lookups? That is, does e.g. nslookup from the command line or Internet Explorer still work when firefox stop working? The difference here is probably quite important.
posted by rpn at 1:58 PM on October 26, 2007

Response by poster: Yep, only Firefox; as I said, all other apps continue to work fine.
posted by dfan at 1:59 PM on October 26, 2007

One question, are you really restarting firefox, or could it be running without any open windows? I ask, because I find that often when firefox is being wonky, it won't quit properly. Try opening the task manager after you think you have quit and see if firefox.exe is listed on the processes tab. If it is, select it and terminate it, then try running it again.

It might help, even if it doesn't get you to the root cause. I also wonder if firewall software couldn't be causing problems.
posted by Good Brain at 2:05 PM on October 26, 2007

Sorry, missed that sentence. If it's only firefox it's strange. Good Brain is right, check that no firefox-processes is still running when you try to restart it.

I've never had this exact problem, but with some similar problems with problems with firefox just trying to exit firefox still left the process running in the background (and starting firefox again just asks the old process to open a new window, which means the problem is still there).
posted by rpn at 2:09 PM on October 26, 2007

It is a firewall issue according to other sites. I don't recall detail, but I had this and it took me a while to realise it was the firewall in my wireless router which was at fault. Google and you will find more - it wasn't hard to find when it happened to me and it is a quite common problem iirc
posted by A189Nut at 2:11 PM on October 26, 2007

I have a similar problem on my laptop. Frequent 'firefox cannot find the server at...' but its not just Firefox, its IE too. I don't have to reboot though, just refresh a few times. It happens to all sites - even google.
I'll definitely be watching this thread for a solution.
posted by missmagenta at 2:18 PM on October 26, 2007

Try here
posted by A189Nut at 3:42 PM on October 26, 2007

Response by poster: A189Nut: Yeah, that's where I found the advice to turn off IPv6. I did have an old copy of Norton AntiVirus that I now think I have disabled completely; we'll see if that helps. I'll use this EnumProcess program if it happens again and see if any other security-type programs are running.

I'm pretty sure that I've checked in the Task Manager that firefox.exe isn't running any more when I close it down, but I'm not 100% certain. I'll verify it next time.

Thanks for the suggestions, everyone.
posted by dfan at 6:14 PM on October 26, 2007

Best answer: Did you use the Norton Removal Tool to get rid of the old copy of NAV? Norton's uninstallers are notoriously slack.

My standard procedure for getting rid of a bad infestation of Norton is use the Removal Tool, then reboot, then search all local hard disks for folders with norton or symantec or symnet in their names (including searching hidden and system files) and delete them (there's usually still a handful there), then use something like ccleaner to get rid of the resulting dead Registry entries, then reboot.

That thing with the Firefox process that continues to run in the background even after Firefox has been closed: it often seems to be wonkly Java applets that makes that happen. If you've closed Firefox down and you've still got a coffee cup icon in the system tray, that's a big clue. Using Task Manager to kill the firefox.exe process makes the coffee cup go away when you float your mouse over it, and Firefox is usually then trouble-free on restart.
posted by flabdablet at 11:03 PM on October 26, 2007 [1 favorite]

I have been having this exact same problem.
posted by !Jim at 12:21 AM on October 27, 2007

I had a similar problem some months ago. I am far from a geek, but I am persistent.

In IE 7, I had constant problems connecting to certain websites. Interestingly, they were among the most visited sites on the web. Google, Yahoo News, etc.

No matter what tweaking I did to my browser, networking, or connection, the problem persisted.

The one "tweak" that seemed to "work" was connecting through one of those online proxy servers that exist to aid people in defeating firewalls. Got me to thinking.

I'd heard of Open DNS before, but wasn't certain as to what it really did. I decided to investigate.

Now, I'm not the person to explain DNS servers, resolution of names, etc. I do have Verizon DSL in remote Idaho (an absolute stroke of luck).

Further, most of the websites that weren't resolving were those that were "personalized." They loaded my personal preferences, username, etc. I wondered; could the DNS server be the issue?

I'm waxing about stuff I don't really understand... The short of it is, I went to Open DNS, signed up, changed my router settings, and I've never looked back. The issue disappeared. Gone.

I would suggest to anyone having selective connection issues, at least giving Open DNS an attempt. It could be your ISP.
posted by private_idaho at 11:31 AM on October 27, 2007

Response by poster: For anyone following this thread, I haven't had any problems since I completely uninstalled Norton AntiVirus a couple days ago. I'll follow up here if it happens again.
posted by dfan at 4:45 PM on October 29, 2007

I had this problem but got around it by setting another DNS server as a backup.

Windows gives you the option of setting a primary and secondary for any network interface. Usually your router IP will be the primary; I use 4.2.2.1 (a public Verizon DNS server) as the secondary.
posted by Ziggy Zaga at 10:13 AM on November 1, 2007