We're talking different things. The card that goes in the front is storage. Think of it as serving the same purpose as a hard drive in your computer. It's not memory. It's storage.
When your MPC is playing samples, it pulls them from the compact flash storage card and loads the into memory. Your MPC comes with 16MB of memory built in. A user can add a 128MB memory card to the MPC. These cards have been known to pull out of the socket and cause problems. So if you take off the battery door and pull out the batteries, you'll either see a card seated there or not. If not, then you have a problem with the MPC's built-in 16MB of memory and you'll probably need to take it in for service. However, if there is a card inserted in the memory slot, and it's not fully seated, this could be the source of your problems. Try seating it properly. If that doesn't work, try removing it and booting your machine. This will help you narrow the problem.
Post back here once you've checked it out further.
Sometimes I still laugh out loud about the beat kangz and that time some English dude hacked the Akai marketing website and stole a bunch of pictures of the Ren before it was released.