Edit: Ignore this, better answers below...

*Hopefully someone with more direct knowledge of Automatonism can help, but I would hazard a guess that the Automatonism program is taking the audio device over exclisively and so when PD tries to enable DSP it can't grab the audio device.

I haven't seen this kind of problems in years though.

You could check if there is an option in Automatonism to release the audio device when it's not playing.*