Yesterday I reported that Safari reset on my iPhone frequently. Darcy left a comment that suggested that a hard reset would solve the problem. Sure enough, one simple hard reset later and the problem was solved.
To perform a hard reset hold down the top button and home button simultaneously and about 10 seconds. Note that this is also how you power the phone off. When the "Slide to power off" slider appears, just keep holding the buttons down and pretty soon you'll see the Apple that indicates the iPhone is reseting.
I didn't lose any data--a hard reset doesn't reset the Flash memory.
So, like most problems in computers, rebooting does wonders.