Last modified: 2008-02-05 17:58:24 UTC
With a rename, while the block log remains in name of the old account (and I guess the other logs too), blocks are inherited by the renamed account. To unblock the new account, you have to unblock the old username (trying to unblocking the new gives the "block-id not found" error). Tried on the English Wikipedia as well as on Botwiki (Mediawiki 1.11.1 with some not-so-updated Rename estension).
*** This bug has been marked as a duplicate of bug 7011 ***