Try clear your recente history:

• Clear recent history

Try also disable the hardware acceleration:

Try disabling graphics hardware acceleration. Since this feature was added to Firefox, it has gradually improved, but there still are a few glitches.

You might need to restart Firefox in order for this to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Then perform these steps:

• Click the orange Firefox button at the top left, then select the "Options" button, or, if there is no Firefox button at the top, go to Tools > Options.
• In the Firefox options window click the Advanced tab, then select "General".
• In the settings list, you should find the Use hardware acceleration when available checkbox. Uncheck this checkbox.
• Now, restart Firefox and see if the problems persist.

Additionally, please check for updates for your graphics driver by following the steps mentioned in the following Knowledge base articles:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

• Upgrade your graphics drivers to use hardware acceleration and WebGL

Also:

• Check plugins
• Create a screenshot of the problem

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

Thank you.

You can also check for problems with current Flash plugin versions and try these:

• disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)
• disable hardware acceleration in the Flash plugin

• http://kb.mozillazine.org/Flash#Troubleshooting

Thank you for your feedback! Sorry it took so long. I'm trying disabling my plugins to determine if one of them is causing the problem. I've checked about half of them.

Thanks!

It is usually best to disable all extensions as the first step. Then at least you know if one of them is causing this or if something else is wrong if disabling them all doesn't have effect.