Hi I beleive the PIX interface is fixed at 1GigE and with a 10GE SFP in the switch this configuration won't work, you need to ensure the devices are matched for the same speed and media type Multi Mode (MM) or Single Mode (SM).
I beleive the PIX GE interface is MM so you will need to install an MM 1GE SFP into the switch don't forget that you will also need a GigE Failover Link if you are using PIX Failover.
Chris