I'm glad you asked this question, because finding such an answer has gotten easier in the last couple of versions PAC Control.
For example, if you have 8.2 or older, you will NOT find this option (in PAC Control config mode) under Help > Error Lookup. I use this one all the time and find it very helpful! I'd upgrade right away just to get this (9.0 and newer) feature.
Also, in PAC Control (9.1) config mode, under Help > Command Reference, when I searched for the error code you asked about (-417), I see the page for your "Open Outgoing Communication" (which will return that error if you're trying to open a file that the control engine can't find in the file system), but it's also listed under this relatively new "List of Common Messages."
The list is also in [form 1700, the PAC Control User's Guide which can be found in PAC Control under Help > Manuals > User's Guide or you can download it [URL="http://www.opto22.com/documents/1700_PAC_Control_Users_Guide.pdf"]here](http://www.opto22.com/documents/1700_PAC_Control_Users_Guide.pdf) too.
Thanks for asking and happy debugging!
Here are some links to our current latest-and-greatest (9.1). Be sure you're subscribed to OptoNews do you don't miss the upcoming upgrades.
9.1 PAC Project Basic:
9.1 PAC Project Pro: