Safari crashing/hanging up (spinning wheel)?

I just purchases this 13-inch MacBook Pro (i7 upgrade, 8G RAM) less than a month ago and already I'm having major problems with Safari. I first noticed it hanging up (i.e., refusing to load or allow further input, spinning rainbow wheel) while using the new Yahoo mail, but now it's happening elsewhere -- I even needed to switch to Chrome just now to post this message! In Safari, where the text entry for the body of the message (where I'm typing now) should be, only a gray wheel spun over and over and over.

I reset Safari, to no avail.

This machine is new, was a major investment and I'm kind of surprised to be encountering such difficulty so early -- especially with software that care pre-loaded. I'd like to find out the source of the problem before switching permanently to Chrome or another browser.