Well, that is really interesting. I was playing around with it in the analysis board, and it allows you to castle that way- unless black has already castled on that side, even if the way is clear (rewind the game a bit in the a-board and then play different moves to see). Maybe there's a good explanation for it and it's not a bug, but I can't figure it out. Maybe someone smart will know 
Those big, sweeping castle moves in 960 sure are cool.
Yeah thats interesting. If I do it first then I can do it but he can still do it 2nd. But if he does it first I can no longer do it. That cant be right. How do you know its not a bug?
Could somebody look at my game I currently have going on with DaveMcMasters. Im not asking for help strategy wise. But if you go to the analyze game function check out the Castle it will allow him to do (He's black) with his rook on the D file. Its a crazy castle even by 960 standards. Then it wont let me do the same thing. Is this a flaw with the system or am I missing something?
i'm looking into it for you
After some testing of my own, it appears as if your pieces are still in the way. I can manage to have the analysis board castle you once your other back-row pieces have moved, regardless of who castles first. From the wikipedia page on Chess960 (italicized emphasis mine):
Unimpeded: All the squares between the king's initial and final squares (including the final square), and all of the squares between the rook's initial and final squares (including the final square), must be vacant except for the king and castling rook. An equivalent way of stating this is that the smallest back rank interval containing the king, the castling rook, and their destination squares contains no pieces other than the king and castling rook.
EDIT: Ok, I thought I'd gotten it to work, then I went to try again and it isn't working. Weird.
EDIT (again): Ok, trying some more, I got it to work with a certain sequence of moves. I then tried a different last move for black and it didn't work, even though neither black move I made had any effect on attacking any squares on white's first rank. Weirder, still.
EDIT (the third): Now it won't work even with the same move and without having closed the analysis board!
EDIT (last one for now): It seems as if, once I make the castling move for white on the analysis board, it locks it off as an option. Even if I go back one move and try castling again, it doesn't work, even though nothing has changed. The same does not apply for black castling. Definitely some glitch with the analysis board, it seems.
Thanks for everyones help. I guess im just worried that he will be able to use that castle than I wont. Its a very extreme castle and could really change the way the game is going to played.
Just so all you guys know. I love the 960 by the way and this is first time ive encountered anything even close to a problem. keep up the good work.
The fact you can't castle, even after moving the knight out of the way on the analysis board is a bug. We're working on fixing that for you.
Sorry :(
Could somebody look at my game I currently have going on with DaveMcMasters. Im not asking for help strategy wise. But if you go to the analyze game function check out the Castle it will allow him to do (He's black) with his rook on the D file. Its a crazy castle even by 960 standards. Then it wont let me do the same thing. Is this a flaw with the system or am I missing something?
Could somebody look at my game I currently have going on with DaveMcMasters. Im not asking for help strategy wise. But if you go to the analyze game function check out the Castle it will allow him to do (He's black) with his rook on the D file. Its a crazy castle even by 960 standards. Then it wont let me do the same thing. Is this a flaw with the system or am I missing something?