How much memory are you allocating to the DB and how much to ARServer? I had a similar problem with ARS 6.3 and SQL 2000, I've allocated 50% (500Mb) to the SQL server, and this seemed to fix the problem. The thing that slowed mine down was disk usage (swapping) because it did not have enough memory.
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Mayhem, Chaos and Anarchy
My job here is complete!