I just had to pull my motherboard out to put a backplate on for a new liquid cooling unit. When I put it back together I got the 1 long and 3 short beep code. I reseated the memory, and that didn't help. However, on closer inspection, it turns out that I forgot to plug the power cables back into my video card.
So, yeah, it looks like it's a video code, not a memory code.
I realize that the original post is very old, but this thread is at the top of the Google search result for that beep code.
From an older post the guy had the issue when the power was unplugged to his video card. Perhaps you forgot to plug in the auxillary power plugs or you have onboard that isn't working *shrug*