Just got a core i5 27inch iMac at work and doing a little testing with Apprentice.

It wasn't long before I received this in the shell.

houdini(16124,0x7fff701d2c00) malloc: *** error for object 0x12d811dc8: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug
16124


Thanks,
Alan

Well… could be anything! Helps a lot if you tell what you were doing before.
On a side note, try a newer build and hopefully it won't happen again.

cheers