Vista - Unwanted pop-ups

Hi,

I have been using Firefox for some time now but recently I keep getting
advertisements appearing (normally offering free stuff). In the options the
'pop-up blocker' is marked on and there are no website exceptions. I haven't
noticed it happening on any websites I have visited in particular.

I have anti-spyware which I use weekly. This shows no problems.

Is it possible I have an add-on which is allowing this to happen?

I am using Vista Home Premium SP1.

I posted this question on mozilla.support.firefox a couple of days ago, but
having received no replies, thought I would try this newsgroup.

Thanks in advance for any help.

David

"David Venables" <davidvenables@xxxxxx> wrote:
You may have attracted ad or spyware, even if your anti-spyware does not
report it. The fact that the advertisements seem to pop up in a random
pattern, indicates malware. Do NOT download the offered "free" stuff. It is
neither free nor safe.

In general, anti-spyware programs have insufficient detection rates, so it
is a good idea to download and scan with one or two extra programs. They may
catch what has been missed by your current program. You can give
Superantispyware, Spybot S&D or Ad-aware a try.
Possibly. If so, it is adware or spyware, and may not show up in the add-ons
listed.
Better still, post in microsoft.public.windows.vista.security. There you can
get better advice on malware removal.

Charlie42