Last week, Software Update detected an update to Epson printer drivers. I dutifully downloaded and installed it. A test print was fine but, the next day (after a restart), it was not possible to print anything. Fortunately, my SuperDuper clone had not been updated so I booted into it and was able to print. This showed that the printer itself was not faulty.
At this point, I considered resetting the printing system but I had no way of knowing if that would work because it was possible that the update itself was responsible. Consequently, I manually copied my emails from Entourage 2008 from my main drive to the clone*. Then, I cloned back, booted from the main drive, and all was well. This took less than 10 minutes.
*For those who want to know, Entourage 2008 data are stored in ~/Documents/Microsoft User Data/Office 2008 Identities. Luckily, I had not done much else with my files since updating the printer drivers.
The moral of the story is to always have a backup before updating software. This is the first time that a printer driver update has ever given me trouble so I wasn't expecting it.