no this is not correct chain.. if you resync u will not get on that chain because it's invalid .. but pool carry on mining and those that never stoped syncing stayed on that chain...
possibly corrupt dat file somewhere.. and reorg never work proper..
possibly the same thing happens with namecoin, except they never become a longer chain, so doesn't have the same effect

also possible someone cause reorgs to happen.. we'll try to get pools to put more hash on (they are not going full blast atm, it seems)

still... we'll keep looking into the issue