Tomorrow, LJ is doing a massive server move
and will be offline for four hours (possibly less, possibly more), starting 11 AM EST/8 AM PST. They're also bringing it up slowly, rather than all at once, so it may take a while for all functions to be enabled.
More on this at the link above.
Today might be a good time to back up your LJ: LJ-Archive
and other options are out there.