I have tried some solutions -- like putting Firefox in the 32-bit mode

I use both Safari and Mozilla on my MacAir OS 10.7.3

Tried to download Adobe Reader (although it's supposed to come with my purchased Acrobat 9 XPRO), but I get eh message that "another instance of Adobe is running...." but there isn't.

Obviously this is a problem for many....but Adobe hasn't offered any help other than to go to this forum -- but there isn't any clear cut solution?

I'm having the same trouble, as is my husband.  Downloaded latest Adobe update--and PDF files won't download.  Actually the download window doesn't even function anymore, but it's probably because I'm not able to download anything.  No error message.  Just. . . nothing.  Firefox is the browswer, Lion the OS.  When in Safari, I can access a small menu when I click on the PDF image which will then allow me to save it.  But nothing with Firefox.  Husband contacted his Mac specialist on campus (we're both educators) and he said to access the root level file and remove the Adobe plug-in and then go back to Firefox and install the PDF viewer, but I can't replicate that on my machine.  (Root level?  Really?)  Sounds like a problem.  Can you fix it?

Um.  That's not the problem, because I could go into Safari and use their onscreen tools to download and view.  Apparently this all happened in the last update for Firefox for Macs.  This is how we fixed it (courtesey of our Mac tech on campus):

Go to the hard drive--

Then Library--

Then Internet Plugins.

At the top of the list are two Adobe plugins.

Delete those.  Restart the browser.

It should work fine now.

Again.  There were no error messages.  There was just a blank page and no action in the download menu, nothing showing up on the desktop.  But deleting the Adobe plugins worked.  Hope this can help others!  (And maybe those at Adobe, who might want to be aware of this problem.)

I posted on how we fixed it, in case you're interested.  Over and Out.

Here is a troubleshooting guide that helped me to make it work with 10.8 Mountain Lion, Firefox 14.0.1 and Acrobat 10.1.4:

http://www.pdfshareforms.com/pdf-forms-on-mac-with-firefox/

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and leave forum replies to forum posts which are looking for solution which

will allow delete, copy long path files.

Opquilt ..you are, as Ralph Cramden used to say to Alice, "The Greatest" ...as a researcher the problem described was extremely frustrating...solved now in a nonce with your brilliant, generously offered suggestion...I am in your debt sir/madam....

Fixed it right away. Thank you.