Not sure if this will help because we don't know your complete system specs but you can read a response about the same issue from BMD
http://forums.creativecow.net/thread/124/874078
"Think of everything in terms of building capacity."
Kris Merkel
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Product Specialist, Flanders Scientific Inc.
http://www.shopfsi.com
Co-Founder, Atlanta Cutters Post Production User Group
http://www.atlantacutters.com
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CS 5.5
FCP7 and Studio
Blackmagic Design UltraStudio 3D
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2TB Max Digital Pro Edit2 VR
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1TB CalDigit FW VR
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