Outlook Web Access sends illegal Content-Disposition headers and this is no longer allowed in Firefox 8. The server needs to be fixed.
See:
https://support.mozilla.com/nl/questions/894442
https://support.mozilla.com/nl/questions/895024

i saved the file of e-mail letters from a Web Browser on my desktop by passing the file itself, a shortcut to this file Now the shortcut is not removed nor what methods. shortcut , and so always appear when I save files from the letters. I think this is a problem with Mozilla Firefox 8.0 other options for the problems tested and rejected. I'm sorry for my english

I solved the problem--I downloaded Google Chrome to use instead of Firefox. It does not have a problem with downloading .docx, .pdf, etc. on Outlook. Contrary to what Mozilla has indicated, the problem has not been solved and occurred immediately after I did the Firefox 8.0.1 update yesterday.

It's funny that you mentioned Chrome since it had this Attachment.ashx problem long before Firefox version 8 started having it. Now Chrome has fixed it, but Firefox is bugged with it. Also, note that When Chrome had this problem, It wasn't reliably sending Messages over Live. Some would go through, and others wouldn't even though they show in the Sent folder. Maybe Firefox now has the same issue of undelivered emails.

It will probably be fixed in Firefox 10.

Bug 704989 - add workaround for broken Outlook Web App (OWA) attachment handling Bug 703015 - Outlook web access attachments download as .aspx

"I solved the problem--I downloaded Google Chrome to use instead of Firefox. "

This is rather knee jerk but after reading through all the posts on bug forums and such, the following is clear to me:

• Microsoft is not following RFC standards
• Mozilla Firefox developers are too busy trying to conforms to standards that nobody is following and are forgetting that without users they have no jobs

I honestly didn't want it to come to this but I really don't need to be fucking with the registry, the browser, or (worse) waiting for a rollback on conformance due to this meth-induced death-march of FF browser versioning. That's for open sores users, not the rest of the population.

Goodbye Firefox, it's been a great 9 years but I don't have time for this anymore. Chrome is my new home.

I found the simplest solution for me was downgrading to Firefox 7

http://mirror.informatik.uni-mannheim.de/pub/mirrors/mozilla.org/firefox/releases/7.0/win32/en-US/Firefox%20Setup%207.0.exe

This should now be fixed in Firefox 9 - please download and install it here - mozilla.org/firefox

Regarding this "attachment.ashx" issue.

I found that if the Exchange Server 2010 is upgraded to SP2 this problem goes away. But you must be accessing it from a newer version of Firefox (9.x +), Chrome, or IE.

Here's a summary of what I found:

Using Exchange 2010 (without any Service Packs applied )

    IE 7,8,9 works.
    Firefox 7.x, 8.x  and 9.01 do not work.
    Chrome 16.0 (newest at the time of testing and only one testsd) did not work.

Using Exchange 2010 upgraded to SP2 (I skipped over Sp1 in testing)

    IE 7,8,9 works.
    Firefox 7.x and 8.0 still did not work
    Firefox 9.01 works.
    Chrome 16.0 works.

Hope this helps add a little more clarity to this problem. At least for Exchange 2010 users.