malloc overlap?

[jan@talentex.demon.co.uk]

This question is probably misplaced - sorry about that, but one has to start somewhere, and I think it isn't too far out. Here goes:

I am developing a program that mallocs a struct, which contains a pointer to another struct, which gets malloced. Then I realloc the first buffer to be one element larger and assign something to an element in the second element - and this action overwrites part of the second level struct. After much tracing I am now sure that the buffers somehow have come to overlap. Is this a known error? I imagine that if the kernel had this kind of problem, it wouldn't run far, but surely memory allocation is handled in the kernel?

I hope somebody can point me in the right direction - and thank you for helping! I am not on the list, so please reply directly.

/jan