Oh, no, this sort of thing happens occasionally. It's because we have multiple servers that all hit LJ relatively frequently (for importing and crossposting and stuff) -- we try to keep things under their access limits, but sometimes we trip their "aaaaack there's a site out there that's hammering our servers, block them!" automatic detection and blocking. Previously we'd been whitelisted, but we forgot to let them know what our new IP addresses were after we switched hardware in December.