I see no reason why this shouldn't work in all browsers, here is my css for anchor tag :

.myButton{
background:none repeat scroll 0 0 #FFFFFF;
border:1px solid #D8DFEA !important;
color:#3B5998;
cursor:pointer;
font-size:20px;
padding:10px;
}

Here is how it looks in IE7 :

And here is how it looks in other browsers :

HTML is nothing unusual as well :

<a href="#" class="myButton">Beta</a>

All of this is inside table, this anchor html is wrapped around with :

<tr>
   <td><a>...</a></td>
<tr>

I don't think this has to do it with anything but I mentioned it just in case, so the button is missing border top, any indications what might cause this?