Try the reset described here:
http://kb.mozillazine.org/Problems_printing_web_pages#Reset_printer

Thanks for the reply. I tried the steps. Still doesn't work. It's strange because I can print webpages fine using Firefox. Its just AOL emails and it just started today. I talked to AOL folks and they suggested clearing out cache which I also did but no relief. Tried different printer, still no luck. Wonder if there's some incompatibility between recent Firefox patch/update & AOL's Print Message service. When I attempt to print the email, I can see the service invoked but nothing happens. Normally I get the Print page right away... I might try Firefox's online/chat help since they should be open now...

AOL's Print Message service - ??
What prints when you use {Ctrl + P} to initiate printing?

Is JavaScript turned on in Tools > Options > Content?

Do you have any extensions installed that block or limit JavaScript?
Like NoScript ?

Do you have that problem when running in the Firefox SafeMode?
http://support.mozilla.com/en-US/kb/Safe+Mode
Don't select anything right now, just use "Continue in SafeMode."

If not, see this:
http://support.mozilla.com/en-US/kb/troubleshooting+extensions+and+theme...

Thx for your continued help. When I hit the Print button in an opened AOL email, it appears that a PrintMessage aspx file is attempted to be accessed in mail.aol.com. Up until now it happened so fast that the Print Preview page would open instantly. Now it just seems to hang on the aspx file. Now for some of your other questions. Ctrl-P - prints the screen image of the open email. That's fine except for the screen formatting vs mail formatting. I can live with this for now.. JavaScript is enabled. Extensions - didn't see any installed that would be a problem. Haven't tried the Firefox Safe Mode yet. I'll try that later after I get some other work done. I'll post a status. Thx again for your help....

Do you have popups allowed for mail.aol.com ?

https://support.mozilla.com/en-US/kb/Pop-up+blocker
Look at Pop-up Blocker Options on that page.

I have never used AOL web mail, but some web mail services I have used open a popup window display a "printer ready" page, sans the navigation menu for that service and the advertising column on the right side. Firefox may suppress that popup unless you have that domain as "allowed" for popups.

Pop Ups are allowed...

Looks like a few others had similar problem awhile back:

Leslie Inman Firefox user

When I try to print an email from AOL Mail by using the Printer Icon it goes to a blank screen with the webmail address at the top.

If I print it all it shows is the following for example at the top of a blank page.

http://webmail.webmail.aol.com/32213/aol-6/en-us/mail/PrintMessage.aspx

I'm using the latest Firefox Browser and Windows 7

Wed 30 of Jun, 2010 06:26 PST #

Virginia Yank - I haven't used this forum much so can't navigate it as well as I'd like. Curious if these users had any resolution/answers...

Running in Firefox SafeMode seems to have solved the problem. Still not sure what the problem was, but apparently some new add-on/plug-in caused the problem?

I am having this same problem and it just occurred when my Firefox updated today to Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.2.11) Gecko/20101012 Firefox/3.6.11). Then when I use AOL.com email the print from email does not work. This does work on Safari, so I believe the update has caused this error. What is the fix to this - it is a mozilla error?

By running in Firefox safe mode I avoided the problem. My suspicion is that a recent add-on/plug-in caused the problem. When I get some time I plan on trying to figure out which one...