Penguin & Seal hack

[yacopu]

Hello! I just registered. I usually used to just check these forums for information (quite useful), but I decided to join.
Anyway, I created a hack of Penguin & Seal (Sachen) that reskins the game to Pengo:

I am having a bit of a problem getting it to run however.The game will crash at the SACHEN logo; I'm assuming its some sort of anti-hacking/piracy measure.
It started acting like this after I changed the palettes. The game runs fine if I skip the logo with a savestate. Would anyone be able to provide help with this?