So is there a trick to deleting pm's in this new and improved system? If you have figured it out, can you please give me a hint? (And to steal a line from Allan, it might be good if you pretend you are explaining this to a seven-year old.)

No wait, scratch that... most seven-year olds are computer geniuses who would just re-write the program! Maybe you should pretend you are explaining it to your grandma.