Following yesterday's tax notice, D called the California FTB this morning and set them straight--it was indeed a clerical error, and Team Snout is now officially listed as a non-profit unincorporated association. We can disregard the bill, and don't even have to file any extra paperwork! (Thanks to Loretta, Stephanie, and John at the FTB for their help.)
D also called the hotel at which we stayed in DC about an erroneous extra charge, so in effect, she just spent 45 minutes on the phone and saved us $1,100. w00t! Now we're going to go celebrate by running some errands and seeing Hellboy 2.