Hours after quiting Parallels 2.2.1922 on a quiescent Mac Pro with 16 GB memory running 10.4.8, a 64-bit command line application I have developed only "sees" about 1 GB available, using standard sysctl() system calls to determine this. Rebooting the system is sufficient to reclaim the memory, but this is not a generally satisfactory solution. I have not investigated the amount of memory "seen" while Parallels is running, but from earlier reports I expect it will be similarly reduced.