Hello Benedict,
the problem is related to the code page of your document. With CorelDRAW up to version 11, the CDR documents where using country specific code pages. With version 12, the whole graphics engine and file-format was changed to work in Unicode, e.g. to support characters from around the world, within the same document. When opening a document with X3 / X4, you have a drop-down list in the File > Open dialog box that enables you to select the code page. If CorelDRAW is not able to do the mapping correctly for you, try specifying the correct one in the list.
Hope this helps.
Gérard