I think that the error is inside of Vault.jar functions for "privileges". The function call that is supposed to tell OnTime what groups are supported for by the permissions plugin, is returning an empty set instead of the list of groups.

I think you need to take this up with Vault team. Sorry.

Here is the Vault/privileges function in question:

    public String[] getGroups() {
        Set<String> groups = new HashSet<String>();
        for (Group g : privs.getGroupManager().getGroups()) {
            groups.add(g.getName());
        }
        return groups.toArray(new String[groups.size()]);
    }
I think the last line should be:

        return groups.toArray(new String[0]);