Sigh.
I've quit crying.
The've fixed it. The tech support guy (whose name is Michael, and I've gotten pretty friendly with him; he's VERY helpful) was able to transfer my discussion posts, and I'm now registered under the correct last name (that was why they deleted my first account: they'd switched my first and last names), and it works when I login because I upgraded to IE 5.1. My teacher just called, and she does, indeed, exist, and I'm her only AP student, and she said when I need anything to call her and insist on being connected (she does a lot of other stuff, too, and is very busy). I sent her my assessment essay, and she may get it by today. I have to do the Unit quiz soon and it requires a proctor, but we'll figure it out, she said. I still can't see the PDFs that are the study guides, and key terms, but it's my computer's problem, not their platform; my copy of Adobe Acrobat Reader 5 is apparently nonexistent, even when I try to open it itself and then open the PDFs. Oh well. I'll figure something out.
I also have a lot longer to do this thing that I thought. I thought it didn't matter how long they extended the end date because I was going to Cambridge from July 16th to August 6th, but it ends on August 15th, so I do actually have another week. Sigh.