The read-only error may be on your computer and the skin downloader can not write the new skin to a file that is marked as read-only.
Try this for Windows users:
Open Windows Explorer and navigate to your Aces High folder. Right-click the skin folder and select Properties. Under the General Tab in the Attributes area, if the Read-only is checked or checked but grayed out then all or some of the dot res files are marked as read-only. If it is checked, left-click the Read-only check-box until it is clear and click the Apply button. A confirmation widow will open, select to apply changes to this folder and subfolders and files and then click OK. Click Ok or Cancel to close the properties window. You should be good to go from there.
GL
