Computer Freezes when I Upload on Youtube?

Ok so I have a few videos I want to upload from my backup drive to Youtube, but I notice when I do it uploads real fast for a sec then firefox freezes and regardless if I let it keep going or force quit, it affects the rest of my computer, than my Finder freezes anda couple other programs. It won't let me force quit, the dock gets frozen, and it leaves me no choice but to force turn it off and turn it on again.

I have 15 inch Macbook Pro, I have the latest version of Firefox, I do not think I have the latest version of flash, but then again i've been told that but a lot of the time when I check I DO have the latest version, not much programs are up.

I also did virus barrier and TechTool Pro and it said i had no issues, and I even did Onyx to clear up my computer, and the issue still happens.

What do you guys think it could be? And how can I get rid of this issue?


Possible ideas i've thought of:
1. Something is in my computer, and the programs aren't telling me
2. I need to upgrade my flash (if it truly isn't the latest version)
3. I should move the videos off of the backup drive so it is on my computer
4. Possibly too many things up at once?

 

Well one thing I did was to use the basic uploader. I also noticed using Safari instead of Firefox also helps a lot.

idk other times Firefox works fine so idk it makes no sense.