[LAU] Too many xruns

Hello, I'm trying to record on a new system, and I'm getting xruns. My old system produced no xruns. The problem system runs: Fedora 17 Kernel 3.5.2-3.fc17.x86_64 Ardour 2.8.14 JACK 1.9.8 Intel i7, 16GB RAM, SATA 6Gb/s drives My user ID is a member of the "jackuser" group. Jack is running as: /usr/bin/jackd \ -T -ndefault -p 256 -R -P 60 -T -d alsa -n 2 -r 48000 -p 1024 -d hw:2,0 In 43 minutes I've had almost 6700 xruns. The working system runs: Mandriva 2010.2 Kernel 2.6.33.7-server-2mnb Ardour 2.8.11 JACK 1.9.5 Intel Q9650, 4GB RAM, IDE drives Reading through the CCRMA documentation here: http://ccrma.stanford.edu/planetccrma/software/installplanetsixteen.html It looks like the kernel and jack for F17 are built for "proper realtime priority". What am I missing. Is there something I need to do beyond being a member of "jackuser" in order to operate with acceptable xruns? I think I'll go back to the old system for a while. Thanks.... -- Kevin