Hi Chuper2, and a warm welcome to the forums! 🙂
Could be many things, we should start with this, here's the scoop...
The usual reason why updates fail or mess things up, is if Permissions are not fixed before & after every update, with a reboot... you may get a partial update when the installer finds it doesn't have Permissions to change one obscure little part of the OS, leaving you with a mix of OS versions.
Some people get away without Repairing Permissions for years, some for only days.
If Permissions are wrong before applying an update, you could get mixed OS versions, if Directory is the slightest messed up, who knows!
If many Permission are repaired, or any Directory errors are found, you may need to re-apply some the latest/biggest updates.
May even need to do an Archive and Install if you have room on the HD...
http://docs.info.apple.com/article.html?artnum=107120
I only use Software Update to see what is needed, then get them for real via...
http://www.apple.com/support/downloads/
That way I can wait a week or so, check the forums for potential problems, and get Permissions & such in order
before installing.
Appears to be time for An Archive & Install, which gives you a new OS, but can preserve all your files, pics, music, settings, etc., as long as you have plenty of free disk space...
http://docs.info.apple.com/article.html?artnum=107120