Legacy driver and network drives

On a couple of instances of XP Pro + SP2, our legacy FSFD is not filtering
network driver, even though it appears to be attaching to the redirector
properly.

I tried disabling all other drivers that attach to the redirector device but
still no luck. We can only reproduce it on a couple of XP workstations. On
most it is working just fine.

I think I read read somewhere that the RDR device had changed names or
changed usage, or something.

Can anyone offer any ideas of where to look first?

Thanks!