Index: ajax.js
===================================================================
--- ajax.js	(revision 4000)
+++ ajax.js	(working copy)
@@ -197,8 +197,34 @@
 		if ( s.dataType == "script" && s.cache == null )
 			s.cache = false;
 
-		if ( s.cache === false && s.type.toLowerCase() == "get" )
-			s.url += (s.url.match(/\?/) ? "&" : "?") + "_=" + (new Date()).getTime();
+		if ( s.cache === false && s.type.toLowerCase() == "get" ) {
+			var now = (new Date()).getTime();
+			if (s.url.match(/\?/)) {
+				// Query string exists, check for cache key
+				if (s.url.match(/_=/)) {
+					// Cache key exists, replace the value
+					var parts = s.url.split("?");
+					var params = parts[1].split("&");
+					var newParams = [];
+					
+					s.url = parts[0] + "?"; // Building the new url
+					$(params).each(function (i) {
+						if (this.match(/_=/)) {
+						   newParams[i] = "_=" + now; // Insert new value
+						} else {
+							newParams[i] = this; // Reuse existing value
+						}
+					});
+					s.url += newParams.join("&");
+				} else {
+					// cache key does not exist, add it
+					s.url += "&_=" + now;
+				}
+			} else {
+				// query string does not exist, add cache key
+				s.url += "?_=" + now;
+			}
+		}
 
 		// If data is available, append data to url for get requests
 		if ( s.data && s.type.toLowerCase() == "get" ) {