Hi Pascal.
If this is a Word document it sounds as though you have a tag missing from your target translation in the sdlxliff file (a bookmark in this case possibly relating to the TOC in this document). This would then mean that Word cannot create the target version as it is missing some important information.
if you run the tag verification function in Trados Studio this should highlight where the problem is and you can then fix it after which you should be able to create your target version all being well.
I cant see anything with exactly the same error message on the SDL Knowledge Base, but the following article is similar and tells you how to use the tag verification.