Adobe flash crashes Firefox

I need help resolving an issue that I know is not exclusive to me, but I haven't been able to figure out. I am having a problem with my Adobe Flash player plug-in for Firefox. It crashes whenever I try to view a video. Oddly enough, it works when viewing the website advertisements prior to the video, but the actual video crashes it. Maybe the adverts use a different Flash player? Have tried it on multiple websites to be sure. I downloaded and ran Everest Home as per Stickey's instructions and will include the specs of my computer below. So far I have tried uninstalling and re-installing Firefox, and Adobe Flash. I have the latest versions of both. I ran Cc Cleaner and Malwarebytes. I have tried updating and disabling all the other plug-ins in Firefox to see if there was an obvious conflict. Per the Mozilla help page I tried running Firefox in safe mode and still got crashes. I looked for the conflicting file NPSWF32.dll and could not find it. So here I am. Any advice?

 

Sorry it took so long to reply. I've been trying a lot of things per your recommendations and not having much luck.
I did everything you said to do in your reply post. Uninstalled Flash Player. Re-booted. Ran Cc Cleaner until clean. Deleted Macromedia folder. Re-installed Flash player, Java JRE, and Shockwave player. Still having the same problem.

To answer your questions, the Flash players crashes on any site that has a YouTube video embedded in it. It will play the advertisement video prior to the video I want to watch, then it will give me the error message "Adobe Flash Plug-in has crashed". I send error reports and try re-loading the page but that doesn't help. When I first posted yesterday, the problem was only in Firefox and not Internet Explorer (I had Active X installed for that). Something you had me do today uninstalled that so now when I go in the internet, IE crashes on any video and any website. I don't really care because I don't want to use that as my browser, but it may help you figure out the issue.
As for the versions and software I have, here is an incomplete list, but should give you the info you need
:
Firefox 3.6.15
Adobe Flash 10.2.152.32
Shockwave Player 11.5.9.620
Java JRE 6.0.240.7

More info: this computer is my Son's gaming computer. He plays on a server called Steam which is in the start-up and runs in the background at all times. He fairly frequently downloads mods and upgrades from this server and when he is done with them uninstalls them. Everything on the computer has been running fine until this week when he downloaded Skype. This did something "funky" to his games and made the computer run really slow so he uninstalled it. This is when the problems began.

At this point, I have completely uninstalled Internet Explorer 8. Firefox still works fine for web browsing, just the Flash plug-in problem. I have read some posts on here about similar subjects and I seem to recall one about some sort of Codec program you can download so you don't need all the different flash and media players. I am willing to try this if you point me in the right direction or if you know the fix for this specific problem that would be great too.

Thanks in advance for any help you can give