[color:"orange"]I just found out that I had a bad stick of RAM.[/color]
Did you test it or just get a memory error? Given your other troubleshooting you've probably tested it, but assuming you haven't;
I've seen RAM become a little loose (especially if the computer is moved around) and start giving errors, but work fine once removed and reinserted.
If you swap the memory still in the computer for what you removed, do you get a slowdown in BD again, or any other issues? The problem may be the amount of memory, rather a fault with a specific piece of RAM (unless of course you have already confirmed it is the RAM).
It could also be a problem with the RAM slots on the motherboard.
There are a couple memory testing programs you can try, if you haven't already;
Memtest86MS Windows Memory Diagnostic[color:"orange"]a new set of 4GB RAM, or <img src="/ubbthreads/images/graemlins/beyond.gif" alt="" /> at full framerate?[/color]
Most RAM has a lifetime warranty, so you should be able to get any faulty pieces replaced.
I had to replace some RAM awhile ago (2 or 3 year old PC120). I brought it back to the place I purchased it because they used to swap RAM out of their inventory, rather than wait for the manufactured to receive it and ship a replacement. Unfortunately, they stopped doing that, but I stole the RAM out of my brother's (unused) computer to keep running at a whopping 512MB (no point in more than that for Windows 98). They eventually replaced the RAM with a better quality brand, but it conflicted with my other piece of RAM. I had to keep my brother's RAM and give him mine (any other combination of RAM in either computer would give memory errors). Dealing directly with the RAM manufacturer might have been faster (though the store didn't charge me anything for shipping).