Oftentimes back injuries on deadlift are the result of poor technique on the squat or press preceding the pull. Without a video it's difficult to say. If you were doing both wrong it's even worse. Probably a good time to see some video.
A follow-up: I tried to deadlift 320 on my heavy day, but it failed again. In fact, I strained so hard that my form broke down and I re-injured my back, which had just become pain-free. This led me to believe that perhaps I was actually suffering from form creep that finally got bad enough for me to fail a lift.
Today, on my light day, I did an aggressive reset (20%) on my deadlift weight. That went ok, and my plan is to deadlift on Heavy and Medium days until I begin to approach my original deadlift weight, focusing on form in the meantime.
Oftentimes back injuries on deadlift are the result of poor technique on the squat or press preceding the pull. Without a video it's difficult to say. If you were doing both wrong it's even worse. Probably a good time to see some video.
Have you every filmed yourself? I like to do it about once a year to check my form.
I'm not sure if I'm willing to post a video publicly... But, after studying my form and other form checks on the forum, I discovered that my shoulders were too far over the bar, and my lower back was not in full extension on all reps. Reviewing the setup protocol for deadlifts in the book helped me a lot.
I've been working my way up through the reset, but I only got 4 reps at 290 lbs before I simply ran out of gas. I had been deadlifting 3x a week, and dropped that to 2x a week, increasing by 10lbs each time. In the meantime, my squat has worked up to 290 lbs. As my deadlift approaches its original weight, I'm finding that I can probably only deadlift 1x a week, increasing 5lb/workout, which will mean that my deadlift and squat will be equal.
I've read that this is not great. Should I simply continue working on my lifts independently, allowing it to eventually sort itself out, or should I pause on my squats to focus on my deadlift?
I think you need to post a video of both squats and DL. If you can squat 290 to depth, then a 290 DL shouldn't present any issue. So, either your squat isn't to depth, or your DL form is bad. I struggle to squat more than 255 to proper depth, but I can pull 380.