Ok, after some more testing I found out that the Stoke error comes from attempting to query the channels layout when there is no valid PRT file.
In Maya, the first frame is typically 1. In Max, the first frame is 0. So when you save a PRT sequence to disk, you have frames 0001 to something.
If you make a PRT Loader in Max and load that sequence and try to pick it in Stoke while on frame 0, Stoke will fail because it cannot ask for the channel layout of a missing PRT file (it should not crash, we will look into that).
In the KMX PRT Loader, just check the "Limit To Custom Range" checkbox and press the "Range" button to set the start and end frames to the existing valid frame numbers (start would be 1 probably). This way, when Stoke asks for the channels layout on frame 0, it will get frame 1 instead and will be happy!
I have logged the error message, but I hope this workaround will let you work with your particles without the need to resave them. If you have issues with the format of the ID channel though, then you need to update to KMY 2.3.
Borislav "Bobo" Petrov
Thinkbox Software Inc.