-moz-opacity : UserChrome in Firefox 1.5

When I add these lines to the userChrome.css the title of any folders (in the bookmark toolbar) disappears after they've been opened.

This worked in Firefox 1.0.7 but not in 1.5.

.bookmark-item > .toolbarbutton-text {
  -moz-opacity: 0.9;
}

Every value below 1.0 gives this result....

How the heck am I supposed to lower the opacity of the text now!?

Any ideas?