Jquery hover lock up

This imageswitch fade animation locks up sometimes when mousing out and leaves the 'facebookblue.png' in place until the next mouseover?

$("#facebookrollover").hover(function(){  
   $("#facebookimg").stop(true, true).ImageSwitch({NewImage:"facebookblue.png",  Speed:200});
},
function(){
   $("#facebookimg").stop(true,开发者_如何学运维 true).ImageSwitch({NewImage:"facebookgrey.png", Speed:400});
 });

And the html part:

<a id="facebookrollover" href="http://www.facebook.com"><img id="facebookimg" src="facebookgrey.png" alt="Facebook" /></a>

Oh and I'm using the imageswitch jquery plugin, but I doubt that that is the problem, since I get same problem when just changing the opacity.

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You could do this with only css: place two img tags inside a one hidden by default, and switch therir display property on :hover. Or even better combine them in sprite and just change background-position.