I'm in the same boat, won't charge but flashes red. Got the same answer from the manufacturer as you did. Bought the cube off e-bay so I guess I got what I paid for. Did you find out how to open it? It's probably just a bad battery!
I recently found a few pictures someone took of it apart. They say they then chucked it into the garbage. I got mine apart last night. There are 8 (1/2 inch) pins along the lip of the seam (two per side) when you carefully separate it. I am still figuring out how they got them in there and sealed.
I removed all 8 pins (they can never be used again, I bent them), but the side came off. You will see four computer connectors holding it in place. Mark the outside of the cube (with masking tape) so you can put it back on correctly. Remove the connectors, remembering somehow which one goes where (I used a sharpie). Once the side is removed, you will see four screws holding down some of the electronics inside. Removed them and the black framed part. There is the battery. It is a AAA Ni-MH 4.8 volt 8mAh battery. I am still looking to see if my local electronics stores (it looks like a cordless phone battery) have them otherwise I will have to build one.
Until I am able to get the battery I wont know about its reassambly. I might either use hot glue or just a few strips of clear tape to seal it back together. The 8 pins are not easy to replace as far as I can tell.
When I get an unpdate, I'll post again
San Francisco, CA