I got hit with this error last week when an IPC event that I was using within my workflow to kick off another workflow process failed to start. It turns out that I had forgotten to give my child process start permissions within the K2 server. As soon as I did this it started working for me.
It seems like such a small error but took way too long to find a solution as there was only a couple of forum posts with the same error as me but without a solution so I can’t be the only one out there having problems with it. Here’s hoping that the next person with the error will stumble across this post rather than searching in vain.