Were you using Adblock Plus or another ad blocker before? The Refresh feature removes all extensions, so that could explain the ads appearing when they didn't before.

It's also possible that you contracted some malware, perhaps in the form of a bad add-on. Here's my suggested procedure for tracking down and cleaning out ad injectors. Sorry for the length -- it's not as bad as it looks:

(1) Open the Windows Control Panel, Uninstall a Program. After the list loads, click the "Installed on" column heading to group the infections, I mean, additions, by date. This can help in smoking out undisclosed bundle items that snuck in with some software you agreed to install, as well as innocent-sounding programs with misleading names. Take out as much trash as possible here.

(2) Open Firefox's Add-ons page using either:

• Ctrl+Shift+a
• "3-bar" menu button (or Tools menu) > Add-ons

In the left column, click Plugins. Set nonessential and unrecognized plugins to "Never Activate".

In the left column, click Extensions. Then, if in doubt, disable (or Remove, if possible) unrecognized and unwanted extensions.

Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Any improvement?

(3) You can search for remaining issues with the scanning/cleaning tools listed in our support article: Troubleshoot Firefox issues caused by malware. These on-demand scanners are free and take considerable time to run. If they finish quickly and especially if they require payment, you may have a serious infection. I suggest the specialized forums listed in the article in that case.

Success?

By the way, the Refresh feature usually is suggested when Firefox is sluggish. But sluggishness has many potential causes and if Firefox was otherwise working well before, you might want to revert/undo the Refresh. That's easy to say but unfortunately has many steps.

As you may have noticed, the Refresh/Reset feature copies your settings (profile) folder to the desktop into a folder named "Old Firefox Data". Check inside "Old Firefox Data" folder for a folder with a semi-randomized name. If there's only one, that probably has your old settings and add-ons. If there's more than one, you'll want to work with the one that was updated most recently.

Once you have identified the profile folder you want to restore, here is my suggested "old profile resurrection procedure":

Overview

These are the steps:

1. Create a new Firefox profile
2. Remove everything from that new profile folder
3. Copy in everything from the old profile folder

Create a new Firefox profile (Windows)

Exit Firefox and start up in the Profile Manager by pasting the following into the Start > Run dialog and pressing Enter:

firefox.exe -P

Note: Any time you want to switch profiles, exit Firefox and return to this dialog.

Click the Create Profile button, assign a name like OldSettings, and skip the option to change the folder location. Then select that new profile in the dialog and start Firefox.

Open the New Profile folder in Windows Explorer

Firefox in the new profile should look like a factory fresh installation. Open the Troubleshooting Information page using either:

• "3-bar" menu button > "?" button > Troubleshooting Information
• Help menu > Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table, click the "Show Folder" button. Firefox will launch your brand new profile folder in Windows Explorer.

Leaving that folder open, switch back to Firefox, and Exit. When Firefox closes, the profile folder should be front and center, or you can activate it using the Task bar.

Copy Old Data in Place of New

In that new profile folder, select all the contents and delete.

Leaving that window open, open or switch over to your Old Firefox Data folder. Drill down into your old profile folder. At this level you should see a folder named bookmarkbackups among other things.

Select everything (Ctrl+a) and Copy (either right-click > Copy or Ctrl+c).

Switch to the empty new profile folder in other window and Paste (either right-click > Paste or Ctrl+v). This may take a minute since some of the files are large.

Start Firefox

Firefox should start up in that new profile with the resurrected old profile data. Success?

At this point, you can pick up where you left off, or just use it for reference/comparison in building up your newer profile.