Did you see if was download anything?

An Idea: Some software during the install process there are some options to install other addons, and when the installations finish they try download that addons, can be it or yes can be malwares too.

Try scan your PC:

• Problems caused by malwares

I have downloads I start going to a download folder, and there is nothing there. I've done scans with MalwareBytes, Windows Defender, Microsoft Safety Scanner, and MS Malware Removal Tool, but none of them find the problem. In Firefox, when I go most websites, either MalwareBytes says that it blocked two malicious sites or I can see it trying to connect to something else. The last thing happens in IE too. Also, very suspicious popups appear telling me about browser extensions or tp speed up my connection.

Hmm try use a pop up/ads block, this popup are ads

• Adblock Plus Pop-up Addon
• Adblock Plus
• More results

I had already run MalwareBytes and MS Safety Scanner. I ran SuperAntispyware and that found some more stuff - one was critical. I had it remove everything it found. So far, that seemed to fix the attempts to go to other websites. I still have the problem with the popups and the strange thing about the download arrow.

And I'm still going through the other possible solutions, thanks.

...later

TDSSKiller didn't find anything. ADWCleaner found a lot of stuff, but didn't fix the problem.

AddBlock Plus seems to have fixed the popup problem.

I still have the suspicious download arrow symptom. (but only on some websites now. This page is one that has the suspicious download arrow.)

Hi Judson, I don't understand what you mean about the download arrow toolbar button moving to a different location. Is it possible to capture a screen shot showing where it ends up and what it looks like there? This article has tips on that: How do I create a screenshot of my problem?

OK, I did a screenshot and cropped it. A couple of seconds after a webpage seems to have finished loading, the big arrow moves across the screen, as it does when I start a download. However, I haven't started a download. It moves to the upper right, where the small download indicator arrow is, as it does with a legitimate download.

Sometimes a problem with Firefox may be a result of malware installed on your computer, that you may not be aware of.

You can try these free programs to scan for malware, which work with your existing antivirus software:

• Microsoft Safety Scanner
• MalwareBytes' Anti-Malware
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

Microsoft Security Essentials is a good permanent antivirus for Windows 7/Vista/XP if you don't already have one.

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Did this fix your problems? Please report back to us!

I haven't tried Hitman Pro or ESET - I will. Thanks.

Try to disable hardware acceleration in Firefox (you need to close and restart Firefox).

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Hardware acceleration was already off. And the download arrow thing happens in Safe Mode too. Sometimes it is gray and sometimes green.

Any chance that one of your add-ons creates this unusual display? To bypass extensions, you can try visiting the same pages in Firefox's Safe Mode.

You can restart Firefox in Safe Mode using

Help > Restart with Add-ons Disabled (Flash and other plugins still run)

In the dialog, click "Start in Safe Mode" (not Reset)

Any change?

No, it does it in Safe Mode too. Earlier I changed all add-ons to "ask before starting".

It only does it on the first website I go to, unless I'm fast enough to go to another one in about 3 seconds - then it does it on that one. It does it once, 5 seconds or so after I start Firefox, regardless of the website.

And many thanks to all of you who are helping! I appreciate it.

You can check for problems with the sessionstore.js and sessionstore.bak files in the Firefox profile folder that store session data.

Rename (or delete) the sessionstore.js file and possible sessionstore-##.js files with a number and sessionstore.bak in the Firefox profile folder.

• Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
• http://kb.mozillazine.org/Profile_folder_-_Firefox
• http://kb.mozillazine.org/Multiple_profile_files_created

Deleting sessionstore.js will cause App Tabs and Tab Groups and open and closed (undo) tabs to get lost and you will have to recreate them (make a note or bookmark them if possible).

That didn't fix the suspicious arrow. BTW, it starts about 8 seconds after starting Firefox, not 5.