If this is not an intentional change by your email website, you might try the following. 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 Ctrl+Shift+r to reload the page fresh from the server.

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

orange Firefox 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:

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

Then try reloading the page. Does that help?

This did not solve the problem. I was able to open the attachments in explorer, but still no luck in firefox.

What kinds of files are affected -- everything?

Is this a popular mail site someone could easily test (e.g., Yahoo, Hotmail, Gmail), or a common corporate product like Outlook Web App? I need more context. Thanks.

To fix this problem you need to reset Mozilla Firefox. To do this, go to Firefox tab at top, click help and then choose restart with add-ons disabled. It will give you an option to either restart in safe mode or to reset firefox. Reset it. I was having this same problem and this solved it for me.

There is an article describing what is saved and what is lost when you use reset: Refresh Firefox - reset add-ons and settings. An "Old Firefox Settings" folder will appear on your desktop. I recommend keeping this folder for a few weeks until you are sure that you have everything back to normal.