At first, I noticed the problem on Pale Moon but I quickly tried it on Firefox to face the same issue.

This problem was happening on PM/FF and IE, but it's currently happening on Pale Moon/FF (3.6 - 12).

As for now, IE has been fixed somewhere by an update or some other method that I wasn't aware of, there's still a minor lag but it's not enough to say that it's bother.

Other browsers that weren't affected by this are Opera and Chromium-based browsers. K-Meleon has it a bit, not as bad as PM/FF, but it's a little worse than IE.

This hasn't happen before, so it's Flash or the Youtube site that is messing with Flash, and spiking Firefox. If the other browsers can tame this from happening, it has to be FF that has a fault somewhere, anything we can tweak?

Sorry, it's not a solution, just more information on browsers that work.

Edit: It's close to K-Meleon's lag while using Firefox 12 on Safe Mode with just Flash working, so something is enabled on normal mode that messes it up. Some can be really heavy for the Flash load, so even those are laggy.

Tested by playing a 720p video and typing as it plays.

One solution stated is that we have to have the mouse cursor on the video. For me, it didn't stop the lag but it does lessen it a bit and the page doesn't refresh, cutting-off all that I had typed before the page refreshed, I type fast so that was a lot of input lost during that time.

Ill try that but it seems a bit ridiculous you have to have the cursor over the video! It must be an issue with flash being played. And I don't like Chrome at all, funny that Firefox has better searching using the Googles won searchbar!

Actually, I found the solution (It could be temporary and not that great, but it helps) and posted it in the link below.

http://forum.palemoon.org/viewtopic.php?f=3&t=368&p=1558#p1630

I am anti-Google or I would have agreed with you about the search. I use Yahoo! or DuckDuckGo. :)

Have a good day. :P