bchambers, to BC Forums!
There's a couple of options you can try, have only seen this happen once in my days. It wasn't my computer, so can't say what caused the issue.
1) Boot into Safe Mode, as soon as you press the power button, begin pressing 'F8' repeatedly. If you can get into Safe Mode, chances are you can login. If so, proceed, and reboot. You should than be able to login as normal next time.
2) Press Ctrl + Alt + Delete, a few times if needed, and see if the alternative login screen comes up. If you can login this way, the next time should be normal.
BTW, I happen to have that same make & model of computer, however it's been in storage for well over a year. Hopefully one of the fixes above will get you going, if not, post back, maybe someone else has feedback.