There are a couple of interesting options in the "Edit Personal Information" screen, including one near the end which has as its description. "Send HTML emails. Check this if your e-mail program fully supports HTML in your email. Many clients try to support it but fail horribly. If you uncheck it, LiveJournal will only send text e-mails." Maybe livejournal got confused and accidentally flipped some bits in your personal options section of your account?

There's also an interesting option labelled "Enable message boards. Check this if you want people to be able to reply to journal entries you post." Sounds like this somehow got hiccuped to off when you posted that last transaction, which is maybe why the "reply-to" link disappeared? I dunno..... sounds like there may be some bugs in LJ.
(But I guess you already knew that. <grin>