It turns out, however, that Firefox 2 uses the same function name for their spelling-checking-as-you-type. I had to rename my function.
Okay, so it took me not long to figure out the cause and fix it. But this isn't a JS1.7 change, so it shouldn't be messing with my scripts.
Fx2 is nice, though. It's much faster and less leaky, probably because Tab Mix Plus didn't support it. This means worse tab behavior, but I'll survive. Or I could try the RC.
1 Not so much a spelling checker, as a tag parser for some forums I use. Convenient to type in, e.g., '[Staff]' and have it translate to a link to the staff list.
2 Seafood node 1.