I have a 'stand alone' toolbar which displays properly on all browsers (Opera, Firefox, Safari, IE6 and IE7 and even IE8). The problem appears when I emulate IE7 under IE8 using the meta tag X-UA-Compatible content=IE=EmulateIE7. (I use a google map ..)
This is the result under ie8 in ie7 mode:
and here is the 'proper' version.
I had this problem with ie7 before, but after doing rendering in the proper way, it disappeared. Under ie8 it work properly unless the ie7 emulation is activated.
I found that the problem exists even with the menu example in the extjs distribution: just extend the header to
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta http-equiv=X-UA-Compatible content=IE=EmulateIE7 /> <!------ ...
<title>Toolbar with Menus</title>