Do a malware check with a few malware scan programs.
You need to use all programs because each detects different malware.
Make sure that you update each program to get the latest version of the database before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
• http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page

See also "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked and What to do when searches take you to the wrong search website

Hi there Vance. I have had similar to you, just today, but perhaps my issue which is fixed by the way, may not be as similar in the solution between us. I hope not, and that what I did can work for you, just we having different plug-ins the only difference. Let's hope. Here was my solution:

Firefox was acting strangely last night, and today, I having updated FF just 2 days ago, and a few cleaner programs which I think one re-configured my system default choices I created, so I ended up un-installing my favorite add-ons, and a lot of other stuff to try and figure out why my downloads we suddenly slow like grandma, and timing out if I veered from the download page, which never occurred before, ever. I even changed themes, SO, in doing this, then re-installing my plug-ins, and other favorite add-ons back into Firefox, this had cleared a lot of my configuration sets of programs I had made before this occurred. So like you, a pop up came on each time I logged into FF, yet after I had chosen something to download. It scared me, as my IE (Internet Explorer 8) settings are to block pop-ups at medium, but I hadn't had a pop up in simply forever.

Turned out it was a download manager that couldn't download anything because I had uninstalled it from my Windows 7 Programs and Features, and could only disable the FF Plug-in for this program. I am bothered by the way that FF just doesn't allow users to uninstall many plug-ins, but will only allow them to be disabled, one being Google Updater, another Fresh Device DLM, and a few others. My issue would not have occurred if they did.

Anyway, that is what I did. I disabled the program by going to inside Firefox Tools, clicking add-ons, then clicking Plug-ins, then right clicking the program that sent the pop-up then clicked disable, to re-disable the program once again. There is a chance that one of your installed add-ons is doing this, or maybe there is an installed program you did not authorize that installed itself from a web page you visited recently, as that is common practice it seems these days of some sites, though injust, and an invasion of privacy in my opinion. There are many, even some who are considered respectaable Internet Services who will change your Search Provider default to their choice, like BING. I have quickly grown to HATE Bing, Google has been known to do it, too.

One more thing Vance, which you need to do anyway every now and again, regardless, as due to default Search Engine stealing, you should check Internet Options in your Control Panel to make sure your IE settings are still the ones you configured your Browsers and addons in IE, FF, and Vista to be in the first place. Programs, and web pages LOVE playing around in your Internet Options window. Many years experience with XP, Vista, and now 7 have taught me that. Reset those Browser setting in IE back to your previous choices if you see they have been changed, so then they will be on equal terms, so to speak with FF, as whether you know it or not, IE, and FF are intertwined in a way, that when you download anything, that program will integrate itself in most occasions on BOTH Internet sources.

The best Pop-up blocker FF has in add-ons in my opinion is Ad-Block Plus: https://addons.mozilla.org/en-US/firefox/addon/1865/

But today I am trying out a new one for me, called PageTweak, and it includes Ad-Block, Download Manager, and about 6 other great, useful programs which a user can enable, or not, it's their choice. So far I am loving it, and I have AdBlock included! Here is the link to download PageTweak incase you want to try it, too.

https://addons.mozilla.org/en-US/firefox/addon/193688/

So Vance, it souns to me like this is what happened to you. Some web internet service changed your default settings, AND made themselves your default search provider, and OR Home Page, all of which can be reset by you in Internet Options, in your IE in Control Panel in Windows XP, Vista, and 7.

If you have IE 7, or 8, at the bottom of the Window in Internet Option, where it says Manage Add-Ons, there is a little box you can click, to add a check mark and it says PREVENT Programs from suggesting browser settings Default Search Engine, Provider, and or Home Page. One of those 3. Bless ya Vance, good luck, and have fun!

Xeny