Why is this code exiting to the basic prompt?

["BLuRry" <brendan.robert@gmail.com>]

I've started tracing ballblazer to see why it isn't starting properly.

The observed behavior is that it displays the crack screen and waits
for a key.  Once a key is pressed, the machine jumps right back to the
basic prompt.  (?!!?)

Looking at the disassembled source, I'm even more confused.

7fd: jmp 2466
2466: 6da0.719f > 400 (each byte is xor'd with BB -- this is obviously
the crack screen)
248B: wait for keypress, clear strobe, jmp 2400
2400:  copy 6000.6eff > 6d00 using ZP registers 0-4
[
	m0 = 6d00
	for (m1 = a800; m1 > 5f00; m1 -= 100, m2 -= 100)
		for(y=0; y < 256; y++) mem[(m1)+y] = mem[(m0)+y]
]
2423: copy 2000.23ff > 400
2440: Fill a29d.be9e with 0's  (self-modifying!)
2454: Soft reset (3f2) = 400,  JMP 400
400: Stack Ptr = FF, X=A=0
406: Fill 0.ff with 0's, Fill 200.2ff with 0's
40e: Activate Language Card Ram write
FFFC = 400, 20 = 20, 21 = 1, 22 = 40
42a: Turn on hires fullscreen mode

Now, since I'm not seeing a hires screen, I know that the jmp to 400
never happens.  At least not to the code I saw in the debugger anyway.
If I press ctrl+reset and then 2400g then I see the game appear and all
is happy.

So I can infer only a few things, some of which shouldn't be possible:
1) the jmp 2400 never happens and goes to the wrong place for some
reason (basic, warm-reset, or who knows where?)
2) It does NOT get as far as 2423 -- if I type "2423g" I see the game
appear but it crashes
3) So logically, 1 must be true.  So that means something is odd about
the following:

248B: LDA $c010 ;clear strobe
248E: LDA $c000 ;get key
2491: BPL $248E ;wait for keypress
2493: LDA $c010 ;clear strobe
2496: JMP $2400 ;start game

This doesn't make ANY sense.  But it's logically the only place where
this COULD go wrong!

-B