With revision 19005 some modifications of xp.css was created. Some of them was not backward compatibile.
After update titles of panel tab's apperas with decoration's typical for 'A" hyperlink elements.

Was css modifications really necessary?

In my opinion css changes from revisions 18990 and 19005 can be reverted because I see some problems
- without this changes label on tab works well
- syntax modification is not backward compatibile, tabs are not correctly displayed in IE6
  instead
      .icePnlTbOn .MidMid>a, .icePnlTbOn .MidMid>div {
  can be old
      .icePnlTbOn .MidMid a, .icePnlTbOn .MidMid div {
- css syntax like
      .icePnlTbOn .MidMid a, .icePnlTbOn .MidMid div {
   increase twice size of tab area because div and a got the same big padding
     <a class="icePnlTbLblLnk">
            <div><table cellspacing="0" cellpadding="0"><tbody><tr><td>Tab title</td></tr></tbody></table></div></a>

Finnaly xp.css from revision 18990 was better than 19005.
I don't see any problem's with xp.css without these changes.