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

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

It is possible that your security software is blocking this information or otherwise interfering.

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if this helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/

I followed ALL the Above suggestions to NO AVAIL!

When I start a download, if I then Click PAUSE, it WILL NOT CANCEL & IT WILL NOT RESUME, just sits there stating "unknown time remaining" and I CAN'T GET RID OF IT!

It would seem that Something Changed with the latest Firefox Beta Update that is causing this Anomalie.. Please FIX ASAP as I find this Very Annoying.

With ANY Download in Limbo the Firefox Taskbar Icon displays a Partial Download Progress THAT NEVER CHANGES and I can not tell what Other Downloads are doing - It also Warns me that X-Number of Downloads are Still Pending when I go to Close Firefox, but as I stated, these Downloads are DOING NOTHING & CAN'T BE REMOVED!

HELP! - BJ

hello nedro, yes this is a bug in the current firefox 32 beta 9, which will be addressed with the next update that will be available shortly.
since the original question here is a few months old and must have had a different cause for the issue, i will close this thread to avoid confusion. thank you