Anne,
This very thing has been happen ing to many apple users after updating to 10.6.8. Sure, Apple is never going to admit to it. HOWEVER, there have been a few "fixits" that readers and others have found. There are three things to suggest: 1) stay within this thread and GO BACK through responses . . . you should find a few solutions. To me, "going back" means two or three weeks. 2) go the "macfixit" web site (type macfixit into your browser) and scroll back a few pages until you hit their treatment of this topic . . . they have a solution. This site is run by professionals. 3) you will find that if you put something like 'can't print after os x 10.6.8 update' into your browser you will get some very good help here (this is because this has been so big of a problem involving many people).
In the future, besides always backing up before an update, be sure that you investigate to see if there have been any problems that a number of people have encountered. You can do this, for example, by going to the "macfixit" website, or to this Apple help.
For me, I always use combo updates vs. the software update when comes to updating os X. Further, there is no way that I am updating to 10.6.8 until the bugs are dealt with by Apple---Lion or no Lion.