There is a legacy syntax for path names, which is one letter, optionally followed by one digit, always followed by a slash, followed by the native path name, with some additional restrictions. This was used mainly in SITE.CATALOG but it is also accepted in list headers. A misspelled native path name that looks like the legacy syntax is one way to get this error message. My suspicion is that you have a list with a relative path in the "Notebook=" keyword that looks like the legacy syntax. Maybe something like:

"Notebook= Yes,a/abc/def,Monthly,Public"

The letter 'a' is not acceptable in the legacy syntax and could give you this error. This is just a theory. More context from the log would definitely help.

  Eric