Let's start with the assumption that it's most likely to be a temporary glitch.

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:

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 AOL webmail site:

Tools menu > Page Info > Security > "View Cookies"

Here you can remove your individual aol cookies.

Then try reloading the page and logging in again. Any improvement?

Microsoft Word has a special way of constructing HTML that preserves attributes unique to Word documents. However, when you paste that special HTML into a webmail editor, it may not be interpreted the same by different sites, all of which want to cleanse dangerous elements from that HTML. Maybe AOL has changed something? Do you know whether the messages appear blank in other browsers?

As a temporary workaround, if the messages do not contain embedded images or other non-textual elements, you could strip the HTML formatting by first pasting into a plain text editor such as Notepad, then copying from there and pasting into your email. To restore formatting (e.g., bold, italic, underline), you would need to use your webmail program's tools.

Finally, I'm not familiar with Firefox 5.1.9. Could you double-check that version number?

My error - meant Safari 5.1.9

Problem only takes place when using Firefox to send AOL emails with text pasted in from a Word document. To test it I sent myself emails and no text appeared in the message. This includes sending emails from Gmail to AOL with text pasted in from a Word document. No issue using Safari. Will try your solution.