I tried it on another computer with Firefox (with no extensions installed) and instead of bringing up the red error box, it just went straight back to the login page (i.e., no visible feedback other than the postback). And it works fine with Internet Explorer on that computer as well.
The weird thing is that it *was* working the day before, and, without my changing anything, it stopped working. I changed the theme but it didn’t make a difference.
Any ideas? (And let me just say that I absolutely love WordPress and have been extolling its virtues to everyone I know. Even if this does happen to be a bug, I’ll still love WordPress just as much as ever. It’s good software — like the thing at the bottom of the page says, it’s poetry. :))
