At my work we just fought a huge virus outbreak that was spread through the symantec corporate antivirus client.  We ended up finding two new viruses that weren't being detected by Symantec and were using a vulnerability in the client to spread.  When we submitted the new viruses to symantec they indicated that a lot of their customers were affected by it.  I'm located in Tulsa, we get calls about every other day from a 'friend of a friend' that is fighting the same virus and wanting help shutting it down.

So yeah, all software has bugs.