Me neither. Rule Of Rose uses i3d as well. A guy on Twitter named @MurugalStudio has reverse engineered the format.
Looking at the file in HxD doesn't give me anything to go on really. A German forum thread talks about corrupted format because of the values using ä ö ü
With the Notepad ++ you can open this damaged map01.i3d in xml format, then you can see if strange characters that do not belong to our alphabet have suddenly crept into the texts. The error is then present there in the named object.
However I have no idea if it's that easy of a fix.