removing active application in the launcher make unity crashes

By remove do you mean drag it outside of the launcher? This does close the running application for me but I don't see a Unity crash.

yeah, it crashed for me.

please re-open if this is still an issue, I'm unable to reproduce it with this weeks release

This bug was fixed in the package unity - 0.2.30-0ubuntu1

---------------
unity (0.2.30-0ubuntu1) maverick; urgency=low

  * New upstream release fixing those issues:
    - clicking on an app window in workspace switcher does not get it to focus
      (lp: #612327)
    - App name stays in panel after exit (lp: #613087)
    - Bright line at the bottom of the launcher bar (lp: #613084)
    - additional round corner when clicking on application places item
      (lp: #612542)
    - removing active application in the launcher make unity crashes
      (lp: #612535)
    - Intermittent loss of all input (lp: #607519)
    - Wallpaper picture-options are not all taken into account (lp: #605788)
    - Add some sort of hint that the Ubuntu circle is click-able (lp: #592787)
    - doesn't render appmenu accelerators correctly (lp: #601011)
    - should highlight the selected items (lp: #600946)
    - Files Place displays mimetype icons for file items when
      thumbnails are available (lp: #599896)
  * debian/control: build-depends on libxcb-icccm1-dev and libutouch-grail-dev
 -- Sebastien Bacher <email address hidden> Thu, 26 Aug 2010 18:31:40 +0200