Groupon Trapped Me - Can't Withdraw My $1000 Unless I Process More Orders

I got involved with a site called Groupon, thinking I could do some e-commerce. At first, it was small $3-5 product orders coming in. Then larger, more expensive orders started coming through.
Little by little, I ended up depositing $1000, and now my money is stuck in their system. A new order came in, but because I didn't process it, they're telling me I can't withdraw my funds. That's what they're claiming.
This seems like a scheme to trap people's money unless they keep processing more orders. I'm really worried about getting my $1000 out safely. Has anyone else dealt with this Grouponshop site before? I could really use some advice on how to approach this.