I think all DAOC settings are saved to text files on your hard drive. It might be some kind of weird Windows permission issue where the DAOC executable doesn't have the right to modify those files under your user account. Try right clicking your DAOC shortcut and select Run as administrator. If you are then able to change your settings successfully, you'll know that's what the issue is. If not, I'm not sure what it could be.
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GW 2: Next!
DAOC [retired]: Meddyck R11 Cleric / Meddyck R11 Druid / Alysson R11 Minstrel / Alyssen R9 Eldritch
Other cancelled MMOs: WAR, SWTOR