Although, the question is fairly old, I'm adding info not present in other answers.
The OP is using stop() to stop the current animation as soon as the event completes. However, using the right mix of parameters with the function should help. eg. stop(true,true) or stop(true,false) as this affects the queued animations well.
The following link illustrates a demo that shows the different parameters available with stop() and how they differ from finish().
Although the OP had no issues using JqueryUI, this is for other users who may come across similar scenarios but cannot use JqueryUI/need to support IE7 and 8 too.