So does anyone know why IE flips out and does weird white/black rendering artifacts when displaying backgrounds in table cells that are specified using CSS.

e.g:
.header1{
background-image : url(../images/headergray.gif);
background-color : #999999;
font-size : 15px;
font-weight : bold;
color : #FFFFFF;
font-family : Arial,sans-serif
}


the double rendundancy is to compensate for netscape's flakiness with background-color. The problem only appears on NT with IE 5. Any help/workarounds would be nice.

-M