Hi Jarrod,
I initially composed all this in an email to you, but when I discovered that I couldn't attach a file to the PM, I'm copying it all here to the thread.
Basically, it happens with all my e-book files on the file open process, and not just the first time it's opened. I can click continue to continue past the error and keep Mobi2Mobi GUI running, but then all fields after Output File aren't filled in. (Didn't they used to be before so you could see what the values were currently set at?)
For the output you requested...
I copied the book over to the directory where mobi2mobi.exe resides as you requested, though I do have that directory in my path as well so for further testing, it probably shouldn't be necessary, unless that's the cause of part of the problem.
This particular file I'm trying to fix the author name on right now (so that it sorts by lastname, firstname on my Kindle), I'm not able to do with the standard --author "Turgeon, Carolyn". I suspect because the author is being stored in that EXTH tag. So I want to use Mobi2Mobi GUI to convert this particular one. (Though as I mentioned above, any file I try is reporting the same error.)
I originally thought it's perhaps it's based on a too long a path to my e-books directory which is "C:\Documents and Settings\Cherie\My Documents\My eBooks" and beneath that are the individual author directories as set up by Calibre. But then I realized that probably isn't it at all since I got the same error even when I copied this Godmother file I'm working on now over to the C:\Util\Kindle Tools directory.
Anyway, I hope this helps to track things down. Thanks!
~Cherie