Fireface 2.898 driver
I've never been able to get SONAR to work on my Acer 7720G laptop with my Fireface 800. dropouts and spluttering every few seconds. I blamed the DPC latency as it has spikes every 15 seconds! I blamed the Ricoh firewire chipset because of its reputation. I blamed the relatively poor graphics. I blamed Vista home premium. I blamed just about everything in turn except the Fireface drivers. I trusted RME and none of the other stuff! Well, since installing the latest 2.898 drivers that came out towards the end of August everything has changed. Everything now works! I can play heavy projects with no dropouts I get reasonably good latency and I can also use SoundForge which was a big no no previously.
So if you have a fireface and had problems in Vista then try the latest driver, it might just work! They say they fixed a memory leak. Well I wonder if that was the cause of the problem.