Can't set preferences, can't sync

Using the last version of Z, I keep on trying to set the options/preferences, but it won't work. This same message (translated from French) shows up for both operations (of course I already tried to reinstall Z):

" XML analysis error : entity not defined
Location : chrome://zotero/content/preferences/preferences.xul
Line number 566, Column 2 : <prefpane id="zotero-prefpane-cite"
--------^

I don't see why chrome is involved as I use Firefox...
help !
Thank you
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