Well, its fixed now, but I'm not sure exactly what did it. I went through a series of restarts deleting, reinstalling, and updating my display driver (NVIDIA), and it didn't work. Then acad's "performance tuner log" popped up and told me to run 3DCONFIG (see below). So I did, and checked for updates, and it downloaded the latest list. Also, under "manual tune" I hit "reset to recommended values" and all is well now. I don't know how anything got changed because I've never been in there before. But at least it works now.
Performance Tuner Results Log
Version: 18.0.0.4
Date of Last Tune: 10/4/2009
Machine Configuration
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Processor Speed : 2.5 GHz
RAM : 4062 MB
3D Device
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Name : NVIDIA GeForce 9600M GT
Manufacturer : NVIDIA
Chip set : GeForce 9600M GT
Memory : 2271 MB
Driver : 7.15.0011.7932
Your machine contains a 3D Device that is not certified.
As more graphics cards and 3D display drivers are tested, they are added to a list on the Autodesk website.
You can check for updates and download the latest certification list at any time. Run the 3DCONFIG command and click the Check for Updates button.
Current application driver: Software
Current Effect Status:
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Enhanced 3D Performance: Not recommended and on
Smooth line display: Not available
Gooch shader: Software emulation in use
Per-pixel lighting: Not available
Full-shadow display: Not available
Texture compression: Not available
Available application drivers and effect support:
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Software driver
Effect support:
Enhanced 3D Performance: Not applicable
Smooth line display: Not applicable
Gooch shader: Software emulation only
Per-pixel lighting: Not applicable
Full-shadow display: Not applicable
Texture compression: Not applicable
Direct3D driver: Not Certified
Effect support:
Enhanced 3D Performance: Available
Smooth line display: Not applicable
Gooch shader: Available
Per-pixel lighting: Available
Full-shadow display: Available
Texture compression: Available
Enhanced 2D Performance: Available