Apple Thoughts: Security Update 2009-0001 Problems Found

"Over the weekend, the mailbag caught a few notes of problems starting up once Leopard users had applied the 2009-001 Security Update (thanks @danielbru), and on Friday the spotty issue was noted by MacFixIt as well."

I haven't had any of the problems that some are having, but apparently they are out there. MacFixIt has an article on it as well, and they offer some tips for fixing the problems (such as "boot disk not found" and disabled keyboard and mouse) that have been encountered.