The problem is in develop mode only. They look fine in the grid and loupe views and when I export them as well. I can also edit them normally, although it's hard to see what I'm doing. Also, all my photos are taking a lot longer to load now as well. What gives? I've restarted my computer but it didn't help. Thanks!
This is likely due to problems with your graphics card driver. Try disabling the hardware acceleration.
Set the option to off and restart LR to see if that fixes the issue. If yes, you might try to see how far you can go with the custom settings by slowly re-enabling stuff until the issue reappears.