The first thing to check with TMX files is
whether they are valid XML files. If they are not valid XML, then
DVX will not import them (and they are not valid TMX either).
The easiest way to check this is to rename the file and give it
a ".xml" extension. Then open this file in your favourite
Internet Browser. If the file is valid, it will probably take
some time to load and it will display the TMX file in some sort
of tree view. If it is not valid, then it will point out the error.