Tracing a memory error on unix

[danielsbrewer]

Hi there,
I hope this is not a too general question. I have a reasonable large program and recently when I run it I get the following errors:

*** malloc[566]: error for object 0x1f2cb0: Incorrect checksum for freed object - object was probably modified after being freed; break at szone_error

Program received signal EXC_BAD_ACCESS, Could not access memory.
0x900042a8 in free_list_remove_ptr ()

Now i have no idea how to trace this back to its source. I am using gcc 3.1 on Mac OS X. I have tried doing a backtrace in gdb but the thing that is points to is clearing a valarray which i have had no problem with previously.

Any hints would be appreciated,

Dan

PS Here is the backtrace: