table tr hover - th bg change

Ok, I am using IE7 - I created a table with multiple rows and a header along the left (it could be on the right also) and then set the following styles to it:

table.calendar td:hover {
background-color:#CCCCCC;
}

table.calendar tr:hover th{
background-color:#CCCCCC;
}

So when you move around the table the cell and the row header gets "highlighted". However, this only seems to be working when moving down the table not up (except on the first row). In firefox it works fine (this isnt supported in IE6). Any suggestions for IE7?

Thanks in advance for any help.