I had a similar situation - I was building an entire area raised up on top of clay. A nurseryman friend had some bog soil from a nearby lake area and thought that would be great to add to my beds. Well, it mixed with the sand and compost and stuff and created huge chunks of concrete like stuff. He ended up bringing some professional soil busting equipment in and working on it. The long run was after a couple years, a lot more compost and other dirt and stuff, it all worked out. But mine is a couple feet built up over top of the clay, not raised beds.
I am sure someone has been through what you are doing and can help - hang in there!
