Thank you Atarikai.
Setting a larger buffer in jack helped. I was trying some jack presets that worked OK previously, so I didn't think that was the problem. But I probably was mixing up the presets. I get the message "audio stuck" in pd, but can connect anyway. Still seem like I cannot go as low in latency as I seem to remember from before with this soundcard, but maybe I'm wrong. Thanks again.

Hello. I have a similar issue. Running Ubuntu Lucid and pdextended 0.42.5. When I try to connect PD to jack I get :
error: JACK error: JackActivationCount::Signal value = 0 ref = 3
audio I/O stuck... closing audio.

I tried different kernels, also RT with same result.
Alsamidi connects ok.

Audun