HI Phillip,
On the other I am wholly unable to download the file from either Safari or Firefox
Let's try one browser at a time. Open a Finder window. Select your Home folder in the Sidebar on the left. Then open the Library folder then the Safari folder. Move the
Downloads.plist file from the Safari folder to the Trash. Relaunch Safari.
If that didn't help, from your Safari menu bar click Safari / Reset Safari. Select the top 7 buttons, click Reset.
Now launch Firefox. From the Firefox menu bar click Firefox / Preferences then select the
Advanced tab then the Network tab. Click: Clear Now.
Relaunch Firefox.
If nothing above has helped either browser, login to your Mac to another user account. Try Safari there. If you can't download files from Safari there, then it's a system wide problem. Boot from your install disc. Run Disk Utility to verify and if necessary, repair any errors on the startup disk.
Help here for Disk Utility:
The Repair functions of Disk Utility: what's it all about?
Carolyn 🙂