Thank you for trying that Rosemary.
I think we have no pretty much established that the cause of the problem is on your server. I strongly suspect that your PHP needs to be recompiled to use a different libxml module. I have you are not familiar with servers that probably sounds like techno-babble, in which case you will need to talk to the server adminsitrator or the help desk of your hosting site and ask them to help you.
Show them this discussion if you like and show them the issue on the Moodle Tracker: MDL-17136
regards
Gordon