Erm ... a much cleaner fix ...

web/root/msgs/management.ssjs

@@ -8,7 +8,7 @@ if(msgbase.open!=undefined && msgbase.open()==false) {
 	error(msgbase.last_error);
 }
 
-if(http_request.query.Action=="Delete" || http_request.query.Action=="Delete,Delete") {
+if(http_request.query.Action=="Delete") {
 	var hdr;
 	var deleted=0;
 	var errors=0;

web/templates/default/msgs/msgs.inc

@@ -53,7 +53,7 @@
     <<END REPEAT messages>>
     </table>
     <br />
-    @@JS:template.can_delete?'<div align="center"><input class="msg" type="image" src="/graphics/delete_messages.gif" name="Action" value="Delete" /></div>':''@@
+    @@JS:template.can_delete?'<div align="center"><input class="msg" type="image" src="/graphics/delete_messages.gif" /></div>':''@@
 </form>
         
 <script type="text/javascript">