Windows 7 stuck in S3 state

I'm hoping somebody can either provide me with a key sequence or a technique to "unstick" my Toshiba netbook. It's been fine for a whole year. Last night, I shut the lid, and this morning, I'm in some weird half-way sleep state and I can't exit it to get a clean boot. After the Toshiba BIOS screen flashes, up comes a plain black screen with a flashing white cursor in the upper left corner. That's all I've ever been able to reach, other than the BIOS utility.

The power button works, and the LED indicator glows steady. The HDD LED indicator glows, and it looks like the disk is trying to do something (lots of hits). It never really turns off. The keyboard responds to Ctl-Alt-Del, but it doesn't change the state. F2 takes me into the BIOS, but there's nothing odd about the settings. Netbooks don't have optical drives, so I can't change the boot order. The netbook has no history of overheating.

Here's what I tried:

- remove power sources and hold down power button for 10-60 seconds to discharge. Reinsert power sources and press power button. No change.
- remove power sources, hold down power button, put netbook in plastic storage then freeze for 15 minutes. Remove from freezer and bag, reinsert power sources and press power button. No change.
- remove power sources, unseat/reseat memory module. Reinsert power sources and press power button. No change.
- press power button on after inserting a mouse. No change.
- press power button on after inserting a bootable USB drive. No change.

I'm fixing to remove the hard drive and mount it in a USB enclosure, then see if I can't access it from another system.

What I really want to do, though, is be able to seriously turn off the machine, so that it will discard any saved state and let me boot clean. I am running out of options.

Any ideas?