Sounds like your machine is running out of RAM, and so has to go to the internal hard drive for more space, known as swap space. What applications do you have running when this happens?
I have a new MacBook Pro 2.8 Intel Core 2 Duo with 4 GB memory, OSX 10.5.6 and I am experiencing a nasty behaviour:
Every so often I get "the beach ball" and the machine stops working. I can't do anything because it is all frozen. It seems that the machine is doing something which is very important and whatever it is, the priority overrules anything else. It is annoying because it may take up to 1 minute (!!) before it resumes its normal functions.
Does any one have an idea what this is and what can be done to stop this?

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