This is also a topic in Wisdom of the Script Gurus but would like to post it here as well since I believe it's a bug.
If I in a script build on to a string (or list) untill llGetFreeMemory() get below a certain point, then clear the string or list, the memory stays below the point where I released the string or list. May sound confusing but if I collect a list then clear it I should get the memory back shouldn't I?