Hi Nima,
Since most of us use AOLserver 4.0.10 I can't think of any immediate answer to your question.
I suggest you do as the original posted on the AOLserver list said, and track down what is causing the increased memory usage.
Is there any reason you need to use AOLserver 4.5 instead of 4.0.10, considering that 4.5 does not seem to work very well for you?