Herve,
I just tried creating a mapping using our wizards when pointed to a hibernate configuration file encoded with UTF-16 and experienced no problems. I’m using MyEclipse 4.0GA and Eclipse 3.1 Final, just in case you aren’t using these versions, I suggest you download and install them before proceeding further.
I think you see this error after the mapping wizard completes and you try to open the generated mapping file – can you please confirm this? Or do you see the error while the mapping wizard is working?
Do you need your generated mapping files to be encoded UTF-16? If not, can you check the Encoding preference under MyEclipse > Editors > XML and see if that says UTF-16? If it does, please change that to UTF-8 and everything will work fine.
If you do need UTF-16, please change the encoding parameter manually in mapping file generated.
Please let us know if you need further assistance.
Best,
Brian.