Q: Xsan Final Cut Drop Frame

Hi there,
I have a problem of drop frame with Final Cut 6.0.6
I have a xsan installed version 2.2.1 (Stornext MDC 3.5.1)
When I tried to edit to tape after 10 or 20 minuts I have drop frame and FC stop edit. If I remove flag in the preferences of Drop Frame I see the drop frames video .
My storage is DDN S2A9900 with two controller in failover. Two MDC stornext 3.5.1 in failover 2 Fibre Switch Brocade 5100.
Someone can help me?...