CSS link background rollovers IE7

Hello experts,

I am using CSS background rollovers in a site main menu as shown below:
It works great, only IE 7 had a problem and for some I have to mouse over the link for several seconds until the rollover background is shown and then again and again& is there any solution for this problem?

div.special-buys a {
float:left;
background-image:url(../layout/left-menu-home/special-buys.jpg);
background-repeat:no-repeat;
width:183px;
height:87px;
}
div.special-buys a:hover {
float:left;
background-image:url(../layout/left-menu-home/special-buys_hover.jpg);
background-repeat:no-repeat;
width:183px;
height:87px;
}