Yep, definitely different standoffs. I'm going to see if it still fits or not with the standoffs removed. The only two standoffs that don't fit are the front two - if the CPU card is bracketed in, then the top cover is put on with the top two screws (the rear two), I don't see why it wouldn't work. I might try unsoldering the standoffs on both units if the board works.
There is one standoff on the 1GB Mobo that touches the board near some traces, so I'm going to put an insulating pad there to see if the unit powers up with the 2GB board.
In regards to the 2GB Mobo with the 1GB card - the left bottom standoff *almost* fits. The right one completely clears the board, so its fine.