There is, without a doubt, nothing as infuriating as memory management problems in C or C++ - certainly enough to make me long for Java or Scheme or some other such language with garbage collection facilities. At least in C++, the potential exists for reference counting (see the C++ FAQ for info), so that memory holes may be made to take care of itself.

One major problem I had (and still do occasionally) concerned the terminating null on strings, which I would routinely forget to allocate or properly reallocate, with disastrous results. ("Dammit, why is free() segfaulting?! There must be a bug in glibc!")