[jQuery] Superfish - negative margin on hover in IE

[Brian]

I would like to put a negative margin on the hover of the LI's in a
superfish jQuery menu on a vertical menu.  When I do this, in IE on
the hover, the elements go below the rest of the menu.  It's fine in
Firefox.

Here's my starting code:

/*** adding sf-vertical in addition to sf-menu creates a vertical menu
***/
.sf-vertical, .sf-vertical li {
        width:  211px;
}
/* this lacks ul at the start of the selector, so the styles from the
main CSS file override it where needed */
.sf-vertical li:hover ul,
.sf-vertical li.sfHover ul {
        left:   211px; /* match ul width */
        top:    0;
}

and I'm just adding this:

.sf-vertical li.sfHover ul {
        left:   211px; /* match ul width */
        top:    0;
       margin-left: -20px;
}

Or even:

.sf-vertical li.sfHover ul {
        left:   191px; /* match ul width */
        top:    0;
}

Both do what I want in Firefox, but there seems to be a z-index issue
in IE....

Help?