Secure Connection Failed

[TeridaxXD001]

Okay, I think I've solved the mystery. It's not "this connection's security has failed," it's "this connection, which happens to be secure, has failed." My connection was slow and poor quality, though still there, so while I could navigate between some pages, others would fail to load sometimes (or in some cases, like this one, all the time). I reset my modem, and voila, I was able to upload the sheet.

In other words, this is a personal problem, and has nothing to do with the site, unless other people are experiencing it. Thanks for listening.