Chris -- how fast are you going? If the wake is right on the back of the deck it sounds like the boat is not going fast enough.... many of us found that there is an inverse ratio to weight and speed (see Ed's note above). not always, but often with more weight you can go a little faster, with less weight you need to go slower. Seems kind of counter intuitive, but you may find with a just little less weight the wake will clean up and be rideable as well. Try with just 3-4 people on the boat instead of 6-7 until you get the wake dialed. Case in point -- I was on the new Epic last year and we had that thing weighed down with full tanks in the back and middle with about 8 people on the back surfing corner. the wake looked horrible. but i've seen some recent fotos where they look like they have the wake dialed in a bit better.
Another thing, not sure if you are doing this, but if you are tossing the rope quickly when you get up, try to hold onto it for a little while instead. Let it get some slack for some time while holding on and just continue to get the feel for staying in the pocket.
Last thing -- in teaching a lot of people, I've found that when starting out, they typically don't use their front toes to lock the rail into the wake. (assuming you are riding frontside). use those toes to keep pressure on the rail to keep the board pointed towards the back of the boat rather than slightly away from the boat. once you are comfortable with that you'll be able to carve up and down the wake and keep the rail locked in just enough to not loose the wake.
Here's an example of what I mean by having the rail locked in. The board is almost horizontal. I'm putting pressure on my front toes to keep the rail dug into the side of the wake.
You can see I'm not the lightest dude out there... but I think I'm on the Shredd Stixx Piranha here...
Anyway, I'm just throwing a bunch of ideas out there.
If you have pics of you riding, post them up and we might be able to give some specific advice.
Good luck!