Are you left-clicking the link when that happens or do you use "Save Link as" the right-click context menu?

Does it also happen if you hold down the Alt key and left-click?

It happens both when I left-click or right-click and 'save link as...'

However when I held the alt key as you suggested, it worked like it should. How do I get the browser to do that all the time?

Start Firefox in Safe Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Appearance/Themes).

   Don't make any changes on the Safe mode start window. 

""Since spaces are not allowed in a URL, the %20 represents a space. If you right click on a link to the file, you should be able to save the file with spaces instead of the %20's. But if you load the file in your browser and then try to save it, it ends up with the %20's."""

Didn't work. I've so far tried re-installing Firefox; diabling add-ons; diabling plugins; updating plug-ins; creating a new profile. The only thing that's helped is, as mentioned in the original reply, holding the alt key whilst clicking on the link. Not a permanent solution though.

Anyone?

How are the files send by that website?

You can check the HTTP response headers with the Live Http Headers extension.

• Live Http Headers: https://addons.mozilla.org/firefox/addon/live-http-headers/

The files are unchanged, I'm not sure what you mean. As I said before the file names come up as they should if I hold the ALT key, but that's not a permanent solution

Still having this problem, and now it won't let me hold 'alt' and click on the download link either...

You can set the Boolean pref browser.altClickSave to true on the about:config page.

• http://kb.mozillazine.org/about:config

Ah thanks for that, at least the temporary solution is back though I'd still love to find a permanent solution.