I don't use Twitter, but can you tell whether it is using an HTTP uploader, like the button below a reply box on this forum, or a Flash-based uploader?

Could you test in Firefox's Safe Mode? That's a standard diagnostic tool to deactivate extensions, hardware acceleration, and some other advanced features of Firefox. More info: Diagnose Firefox issues using Troubleshoot Mode.

If Firefox is not running: Hold down the Shift key when starting Firefox.

If Firefox is running: 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

and OK the restart.

Both scenarios: A small dialog should appear. Click "Start in Safe Mode" (not Refresh).

Any difference?

Thanks. I should have mentioned in my original post that I could upload photos to Facebook in Firefox.

In safe mode, Firefox did exactly what it did in regular mode: It failed to upload photos to Twitter, but loaded them to Facebook.

Lincoln

I finally got into my Twitter account and tested, and it looks like a pretty basic photo uploader.

At this point I only have a general suggestion... 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) Clear Firefox's Cache

"3-bar" menu button (or Tools menu) > Options > 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"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or globe icon in the address bar > More Information > "View Cookies"

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

Then try reloading the page. Does that help?

jscher2000:

Thanks. That did it.

Lincoln