Sometimes when I click in text fields (like to fill out a captcha), I get a pop-up ad and Firefox immediately switches to it, leaving the tab blank.

Question

My problem is pretty much this, if I can explain it well enough: when I click on certain text fields, like to input the answer to a captcha, for instance, I constantly get pop-up ads and Firefox will switch to the pop-up, leaving the entire page that I was on before blank as if I opened a new tab.
This started a while ago and I'd been trying to just deal with it, but it's really starting to drive me up the wall. Is there a fix to this? I'm sure it happened when I went to about:config to try and fix something about text auto-filling. I can't say whether I did that right or wrong, considering my text doesn't autofill anymore, but now I have this annoying problem.
Help?!

Answer 1

Do a malware check with some malware scanning programs on the Windows computer.<br />
Please scan with all programs because each program detects different malware.
Make sure that you update each program to get the latest version of their databases before doing a scan.
*Malwarebytes' Anti-Malware:<br>http://www.malwarebytes.org/mbam.php
*SuperAntispyware:<br>http://www.superantispyware.com/
*Microsoft Safety Scanner:<br>http://www.microsoft.com/security/scanner/en-us/default.aspx
*Windows Defender: Home Page:<br>http://www.microsoft.com/windows/products/winfamily/defender/default.mspx
*Spybot Search & Destroy:<br>http://www.safer-networking.org/en/index.html
*Kasperky Free Security Scan:<br>http://www.kaspersky.com/security-scan
You can also do a check for a rootkit infection with TDSSKiller.
*http://support.kaspersky.com/viruses/solutions?qid=208280684
See also:
*"Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked