Ardour and memory

I have a certain project that I am having trouble with: when I start doing something with it–playing it, editing it, it doesn’t matter what–after a little while my computer slows down and pretty much locks up. I decided to try limiting the locked memory (I had given it unlimited memory before) and now it shows me the box that says JACK was disconnected because Ardour wasn’t fast enough.

So I figure my problem has to do with memory. And the odd thing is that this only happens with this specific project; my others are doing just fine. Have I rigged something up wrong to make it use too much memory?

Any help would be appreciated!