I looked at the spoke heads. They aren't DT. I had thought of replacing the spokes, but if I did that I'd just as soon build a whole new wheel.
When I got home, the wheel was no less true than it was when I trued it during recess today. But the hub is definitely about 3mm further to left the than it is on my other wheels.
I have a few other cheap alex rims which have given me very few problems. But they are either front wheels or track wheels. Go figure. I also have a Mavic MA3 which I've been abusing for a while on my Miyata and it's stayed pretty true as well. I rebuilt that wheel the same way I did the Alex rim.
I took the wheel off my bike and put my new 32mm tire on my near-bombproof Mavic T520 wheel. It will be interesting to see what happens when I respace the hub on the DA22 rim.