I updated from 1.04 -> 1.1.1 too.
I am getting the same problem when trying to connect, console on client side says:
[14:23:43] [Client thread/INFO]: Connecting to 109.xxxx
[14:23:44] [Netty Client IO #5/INFO] [FML]: Server protocol version 1
[14:23:44] [Netty Client IO #5/INFO] [FML]: Attempting connection with missing mods [AromaBackup, BetterTitleScreen, NotEnoughCodecs, notenoughkeys] at SERVER
[14:23:45] [Netty Client IO #5/INFO] [FML]: Injecting existing block and item data into this client instance
[14:23:45] [Netty Client IO #5/INFO] [FML]: Found a missing id from the world aobd:crushedPurifiedMithril
[14:23:45] [Netty Client IO #5/INFO] [FML]: Found a missing id from the world aobd:crushedMithril
[14:23:45] [Netty Client IO #5/INFO] [FML]: Found a missing id from the world aobd:dustTinyMithril
[14:23:45] [Netty Client IO #5/INFO] [MineMenu]: CLIENT: Disconnected from server, enabling all click actions
[14:23:45] [Netty Client IO #5/INFO] [OpenMods]: openmods.network.IdSyncManager.onDisconnect(IdSyncManager.java:124): Disconnected, restoring local data
[14:23:45] [Netty Client IO #5/ERROR] [FML]: Failed to connect to server: there are 3 missing blocks and items
I am the only one playing on the server, and have done nothing concerning mithril, i really have no idea where that problem originates from.
Edit: I should state that i am using the danish version of windows 8.1