Post here with your response, good news, and more so we can solve this issue.
A swirling loading animation means that a routine is in a circular loop. I don't know what caused the loop, but to stop it, press the power button on the upper right hand of the MBP. Hold it down for at least five seconds, or at least until the screen turns black and the computer reboots.
You have several options. You can let the MBP load again, hopefully back to its former self. Or you can press SHIFT continually after pressing the power button; this opens the MBP into safe mode, where you can perform various diagnostics that might be useful.
Thanks for the advice, but unfortunately the SHIFT key doesn't seem to be doing anything to the MBP. It just continues to shut down. I've also tried holding COMMAND, OPTIONS, P and R, but that makes the MBP restart repetitively. It's also starting to heat up faster than it has before. No idea what to do now, except to bring it into the Apple Store. :/
I brought my MacBook Pro to an Apple-approved tech group that thinks the problem may have been generated from AutoCAD 2011. Their guess was that the program was not compatible with the new OS X Lion software. The only solution was to reinstall OS X Lion. They wanted to charge $75 for the reinstallation, and $100 if I wanted to have my data backed up. I thought I'd visit the Genius Bar at the Apple Store before I paid them anything. At the Apple Store they reinstalled OS X Lion at no charge, no questions asked. Now I don't know if it would've cost anything to have the data backed up, since I didn't have anything on the computer of great importance.