You can try this extension to override compatibility issues,

• https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/

The FDM add-on no longer seems to work with FF 5, even after forcing add-on compatibility using the Add-on Compatibility Reporter add-on.

The latest Beta version works, tried and tested :)

[[Free Download Manager 3.8.1041 Beta|http://codecpack.co/download/Free_Download_Manager.html]]

Use flashgot plugin to download with fdm

I want to say that I have tis nasty problem too and the only continous suggestion found in the web is to get the addon You Mozilla guy wants us to use for downloading. I don't want to feel obliged to use just one solution. "You cannot use the program you want! You must use the program I choose for you!"

Not good.....bye bye Mozilla (Firefox, Thunderbird, Songbird, Filezille.....)

....and hope this will be seen within replies!!

@algedi

You can use any download manager that you want, but it has to support the version of Firefox which you are using.

If you are commenting about us recommending Flashgot regularly, it is because Flashgot works with many download managers to integrate them with Firefox. Also because Flashgot is always updated in a timely manner, not only supporting new versions of Firefox before they are even released, but Flashgot typically supports the "next" versions as they are being developed.

https://addons.mozilla.org/en-US/firefox/addon/flashgot/
http://flashgot.net/