Originally Posted by plib
I don't know how this will quote but here is what seems to be the offending passage from the original Word htm file, which was a direct copy/paste from the Wikipedia page.
Yes, this is the same problem, except from the href side instead of the anchor side. The names that my files had trouble with were internal links defining an anchor to use in an href, whereas these are external links used in a href. Same problem. If the links are internal anchors , you can simply remove all the colons in the offending attribute values provided they remain unique which they most likely will be. If they are external urls like these, and you need to link to them you are in trouble unless you can rename the items they are linked to.
In this case you can simply remove the colons and keep the rest of the file. The corresponding external links will be lost but they probably are not included in your epub conversion anyway.
Should repeat: it is too much to expect the Kobo people to fix all problems of this nature. However, they really really should recover from errors of parsing in a better manner, so that a person transferring many documents is told by the Kobo exactly which document it is that the Kobo cannot handle instead of having to work for hours trying to find it by trial and error.