Which version you are using for Firefox? I am using 3.6.2 and I could see all the sites properly with adsense.
Are you sure your site is not compromised on server level?
Recently on one of our office machine we had a malware /spyware problem where we could see a big 728X90 size image banner on top of every site.
That was not detected in any of our anti virus or anti spyware package. (We use a standard anti virus package)

Thanks
Rajiv

Same 3.6.2 and it looks like its blocking adsense ads from all sites, not just mine. It's obviously something connected mostly with Firefox, probably.

A little disconcerting to say the least.

I encounter the same problem since this morning.
Andy

More precisely: the problem is with Firefox 3.6.2 (or any previous version) and Vista, but not with XP. There is no problem with Microsoft OS and any other navigator. And no problem with Firefox and Linux.

I've got 3.6.2 on Vista and on Windows 7, and I'm seeing ads just fine. Are you using a particular plugin or antivirus that might be blocking them?

Also, you want to look at your hosts file to make sure nothing got entered there somehow -

c:\windows\system32\drivers\etc hosts

i'm fine on 3.6.2 with a barrage of add-ons installed (both vista and XP) and have had no problems as yet.

If I where you I would try a fresh install of firefox.

Mack.

I've entirely removed and then reinstalled Firefox a couple of times, to try and get rid of the problem. I'm using the antivirus Avast free. I haven't looked into c:\windows\system32\drivers\etc hosts, because I'm not quite sure _what to look for_ ?

Here is my host file:

# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host

127.0.0.1 localhost
::1 localhost

For me it looks like a hijack since each page with a google ad on it hangs while it tries to connect to 74.55.39.45 I have adaware and McAfee, but that's never a guarantee.

If it was host file related it would effect your other browsers as well.

Mack.

Try running a free scan with prevx and see what it throws up. Malwarebytes and a-squared are very good at removing stuff for free.

Don't know about adsense, but my Firefox 3.6.2 tries everytime to connect to 74.55.39.45 when moving to a new page, and it slows things down a lot. And my virus- and malware scanners aren't picking up anything.

mineman65, try running crapcleaner (it's free)

Ok. Fixed. Unfortunately, I don't know exactly which thing I did worked. I believe that the file microsoftxps.dll was infected. I changed the name to something else.

I also disabled a number of extensions and plugins including the adobe acrobat one, which I think is somehow involved in all this. I have a fair idea of how I was infected since I went to a disreputable site and it opened a php file in adobe acrobat, which clearly shouldn't happen.

I also disabled java extension plug in. If you are stuck I can try to re-enable one by one to see what happens.

By the way I tracked this down using Prevx, but it wouldn't remove them - licence required. I'm not keen on their approach, and wouldn't give them a nickel, since they use a technique that is often associated with viruses, and there's no way I can tell whether they are legit.

I could not find microsoftxps.dll
Are you sure it is the correct name ?

By the way I tracked this down using Prevx, but it wouldn't remove them - licence required.

Yep, I use Prevx to find out the problem then I know what I'm looking for. They are very legit, I install this on every new machine now and have only twice had to pay for a licence for it to resolve a problem I could not and it was done within seconds with no reoccurrences of the problem especially the Facebook stuff that's going on.

The first time I used it two of us had spent 3 hours each trying to sort a problem on a laptop, Prevx did it in seconds...it was immediately added to the armoury:-)

Solved!
Well Prevx did the job. I ran it. It told me there were two dirty files. I did buy for 29 euros the product because I was so exasperated by the bug, and prevx cleaned them. Now Firefox works fine again. (I've no financial interests whatsoever in prevx...)
Andy

Ok. Thanks. I just don't like that particular model, but it found the problem where other programs didnt

Excellent! Prevx did the job. In my case it found a file called Spiral.dll (112 Kb) in a folder called App Data/Local/Spiral and a corresponding entry in the registry.

From the other postings I gather that the malware takes on various names, so looking for Spiral.dll won't help you much. Prevx is free, though.

The free version of Prevx doesn't remove the file and registry entry, but it tells you where they are, so you can remove them yourself.

Worked for me.

Thanks for the tip!

- Rien