Thanks, that however produced the same magic number error. I then added some code to pass back the length of the packed string, so that I won't be reading the engire 1024 bytes every time and read in garbage. That then showed me that on the first call, I'm trying to thaw what hasn't been frozen yet... which of course results in the above error regardless of how you're trying to thaw garbage... So thanks for helping me point in the right direction!