i see...
my brother had the same problem once with a Ruby ROM...
though I can't help you about it, since this computer has no hacking tools, but I do know one thing why it caused that...
Advance Map automatically searched for free offsets, look at the file tab and uncheck the 'automatically search for free offsets'...
then start again from a clean ROM, and then A-Map will ask you for a free offset.
use a hex editor or a free space finder to search for free offsets. ;)