I would suspect that the low memory error message is a red herring,
I've never had low memory messages when playing AVIs and my No 2 PC
has a similar spec to yours.
You could always close down the instances and see if it makes any
difference...I suspect that it won't.
FWIW, I have 7 instances running and I have just rebooted.
I notice that you are running a beta OS too!
** Stress - the condition brought about by having to
** resist the temptation to beat the living daylights
** out of someone who richly deserves it.