Refer to your local Active Silicon Dealer for support and test/repair of the cards.
What exact model are they? (written on the PCB)
Have you put them in a newer Macpro that previously used?
What error message have you seen?
What OS are you using
What drivers are installed?
Is the MacPro running in 32bit mode?
Is this an existing catalys show - or new blank show?
Can create a catalyst system profile?
What o you mean? moving files? what files?
Why would you move a file while catalyst is scaning files?
if scan files causes a crash, then you probably have a problem with a file...
However, these problems sound like a bad or corrupted HardDrive?
Do you have a new HD available and can re-install the OS? - might be worth trying a clean install.
what graphics card do you have installed?
What hardware version of MacPro do you have?
Which PCIe slot is the phoenix card installed?
What other cards do you have installed.
Does the system get particularly hot in its environment? -is there suffcuent ventalation?
Sorry for lots of questions - but may help to diagnose...
Simon