Text cannot be saved: a name may not start with '<', hexadecimal value 0x3C.

I really hope someone can help me with this issue as nothing has helped so far. When I try to export my translation to docx, I get this error message. I already found out that the problem is a mistake in the xml-document. But neither has my xliff converter worked nor could I spot the mistake when I opened the xml in firefox. I'm not really an IT-pro, so maybe someone has an idea what to do? Somehow my xliff converter won't open because it says "I am not licenced". I really don't know what to do. My agency needs this translation and it is already overdue.

Thank you very much in advance for your help!
Rieke Oeldorf