Invoice/Packaging buttons not appearing in some browsers

I noticed a problem with Invoice & Packaging slip buttons on my Mac using Safari. (From Admin -> Orders in rt column). I tested on PC w all major browsers and they only appear using IE7 and Opera 9.5, and they disappear using Safari 3.1 and Mozilla. (They do appear in IE8 but don't work.) Very strange! My first thought then is that it is a CSS issue, as the browsers are rendering differently. The Edit order button always appears.

Has anyone else encountered this. I don't recall installing any contribution that changed the orders.php file, but if it is CSS it could be anything that altered the style sheet I guess.

Please let me know if anyone else is experiencing this or if this is just mine.

Thanks!

Using ZC v1.3.8