Ah, yes that one - ran into it a few days ago
. You should only get that if you are trying to create collections from a boolean column (that's one that only allows true/false). Is that what you are doing?
I was debating whether or not to remove the boolean columns from showing up in the customization section. For now I've left them and I just convert them to the names "True" and "False". Its not a very useful set of names though.
Good to see you got the file to load. Thanks for trying it again, and reporting the problem.
You shouldn't have to know anything about the timestamps on the collections file - the Kindle handles that in the background, as does the plugin. Basically both record the last time you created/opened/modified the collection so it can sort them by most recent in your list. (Sort by Collections on the Kindle is really sorting by most recent, but when the plugin creates the collections it puts fake timestamps on them in order to make them sort in alphabetical order when you first use the Kindle.)