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I'm using Firefox 29.0.1 in a MacBook Pro and in Outlook, I get this message: Error: r is null.

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I have a MacBook Pro, bought in 12/13. I use Safari and Firefox 29.0.1. I have Microsoft Office 2011 and use Outlook for my email. I have no problem with my mail in Safari. However, beginning Saturday, May 24, 2014, I was unable to access Outlook because I got this message: Error: r is null.

I closed Firefox and reopened it. I restarted the computer. Nothing helped. When I opened Firefox on Sunday morning, Outlook worked fine and I was able to receive and send email with no message and no problem. This morning, Monday, May 26, 2014, when I opened Firefox and clicked on Outlook, once again I got this message: Error: r is null. I restarted the computer, but it didn't help.

Once again, there is no problem with Outlook when I use Safari, but Firefox is my preferred browser to use for my email. Please help me in very simple terms, as I am not very familiar with computers beyond email and basic sites.

I have a MacBook Pro, bought in 12/13. I use Safari and Firefox 29.0.1. I have Microsoft Office 2011 and use Outlook for my email. I have no problem with my mail in Safari. However, beginning Saturday, May 24, 2014, I was unable to access Outlook because I got this message: Error: r is null. I closed Firefox and reopened it. I restarted the computer. Nothing helped. When I opened Firefox on Sunday morning, Outlook worked fine and I was able to receive and send email with no message and no problem. This morning, Monday, May 26, 2014, when I opened Firefox and clicked on Outlook, once again I got this message: Error: r is null. I restarted the computer, but it didn't help. Once again, there is no problem with Outlook when I use Safari, but Firefox is my preferred browser to use for my email. Please help me in very simple terms, as I am not very familiar with computers beyond email and basic sites.

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Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

  • Switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance
  • Do NOT click the Reset button on the Safe Mode start window
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Not sure exactly where you have this problem:

For the webmail site, if you haven't already, please try:

When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Bypass Firefox's Cache

Use Command+Shift+r to reload the page fresh from the server.

Alternately, you also can clear Firefox's cache completely using either:

  • "3-bar" menu button (or Tools menu) > Options > Advanced
  • Firefox menu > Preferences > Advanced

On the Network mini-tab > Cached Web Content : "Clear Now"

If you have a large hard drive, this might take a few minutes.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

  • right-click and choose View Page Info > Security > "View Cookies"
  • Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove the site's cookies individually.

Then try reloading the page. Does that help?


In case one of your extensions is involved, could you test the page in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions and some advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

You can restart Firefox in Safe Mode using either:

  • "3-bar" menu button > "?" button > Restart with Add-ons Disabled
  • Help menu > Restart with Add-ons Disabled

Not all add-ons are disabled: Flash and other plugins still run

After Firefox shuts down, a small dialog should appear. Click "Start in Safe Mode" (not Reset).

Any difference?