same for me.. mozilla 3.6 was much faster video, mp3 streaming

Yeah, I agree, I tied downgrading and they kept complaining that it was "out of date" and wouldn't function properly

Dear Firefox 4 users, there is an extension on Firefox 4 called BFlix Toolbar that I removed, and immediately my streaming/buffering was back to normal, meaning that there was no video lagging, and things just generally sped up.

To remove this, go to Tools, which should be up at the top of your screen, and click 'Add-ons.' This should open up a new tab labelled 'Add-ons Manager.' On the left hand side, there should be a list, with 'Get Add-ons,' 'Extensions,' 'Appearance,' and 'Plugins.' Click 'Extensions.' There should be a list, and BFlix Toolbar should be there. Disable and remove it.

I hope this helps! It worked for me, and I sincerely hope it works for you! Have a lovely day/night.

Definitely same problem here. Worked fine pre-4

I had a problem with streaming under Firefox 4: when on youtube, I had the sound but a black screen instead of the video after disabling, and enabling my plug-ins one by one, I realised that the problem came from Tile Tabs, a plug-in used to tile tabs under the same window. I do believe that if you have any plug-in from that kind (it is the case with Split Browser also !!) you just should remove them for moment , and it makes videos in streaming come back Hope I helped

same here on all my 3 of my mac computers.

thanks but everything is still slow, don't know why it is doing this maybe the best bet is buy another computer and get a different internet provider any suggestions

Things started getting very slow through the Firefox 3 series, then 4 and now version 5. Things like BBC iPlayer or News items. I tried Safe mode but it did the same, even after re-installing Firefox 5. At the end of some news items, the video window gets several small pictures across it, listed as 'Similar items'. The borders of each would turn yellow when you mouseover them but I could not access them and... I couldn't see the pointer. I eventually discovered that you could cure the problem by right-clicking the toolbar at the bottom of the screen. I also discovered that 'halting', 'blank' or 'jumping' videos could be unlocked (or at least helped slightly) by doing the same thing. XP Pro - CPU 2.66Gigs - 2 GB RAM - Nothing running in the background apart from anivirus. Any ideas...?

I had the same problem. I have a Gaming set-up. 8 GB Ram,High end G-Force Video Card,Dual Quad Core processors. Adobe & Flash all updated,etc,etc.

YouTube worked great. Even 720p and 1080i Vids loaded fast and played smooth. No lag. Same with Netflix. Watching Hi-Def Instant Watch Vids never Downgraded to a slower/lower bit stream. It only happened with "Live" streams. Like from the local news station and Live streaming shows of various Concerts.

So,I followed the suggestion about Plug-Ins. I removed all of the ones dealing with Zoom/Magnification. Since I never use them anyways. I didn't have any of the ones listed. And just tried those just to see what happened.

I closed FF. Re-opened it. And VIOLA. My live video streaming was back. Synced sound and all. No lag.

I did this on 6/3/12. It worked for me. and my lag was happening with Comcast 20 Mbps service. Speedtest actually clocked it at 17.62 Mbps. Still, it shouldn't have lagged. But I'm good now. Maybe it'll work for you?

PS: I have the latest FF vers. as of the date of this post. (vers 12.0)