Replication 5.1.57 -> 5.5.12 (no replies)

Dear All,

I had set up a replication from our productive machine

--> mysql-5.1.56-linux-x86_64-glibc23
--> InnoDB plugin 1.1.5

to a test box

--> mysql-5.5.11-linux2.6-i686

which ran stable for some weeks. After upgrading both machines to 5.1.57 / InnoDB 1.1.6 (master) and 5.5.12 (slave), respectively, the slave continues crashing with messages like this one:

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[...]
InnoDB: Error: tablespace id is 9523 in the data dictionary
InnoDB: but in file ./thisdatabase/thattable.ibd it is 9668!
110524 11:07:21 InnoDB: Assertion failure in thread 2367437712 in file fil0fil.c line 765
[...]
InnoDB: about forcing recovery.
110524 11:07:21 - mysqld got signal 6 ;
[...]
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 303177 K bytes of memory
[...]
110524 11:07:21 mysqld_safe Number of processes running now: 0
110524 11:07:21 mysqld_safe mysqld restarted
110524 11:07:21 [Note] Plugin 'FEDERATED' is disabled.
110524 11:07:21 InnoDB: The InnoDB memory heap is disabled
110524 11:07:21 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
110524 11:07:21 InnoDB: Compressed tables use zlib 1.2.3
110524 11:07:21 InnoDB: Using Linux native AIO
110524 11:07:21 InnoDB: Initializing buffer pool, size = 256.0M
110524 11:07:21 InnoDB: Completed initialization of buffer pool
110524 11:07:21 InnoDB: highest supported file format is Barracuda.
InnoDB: Log scan progressed past the checkpoint lsn 697841406697
110524 11:07:21 InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Error: trying to add tablespace 9874 of name './dbone/tableone.ibd'
InnoDB: to the tablespace memory cache, but tablespace
InnoDB: 9874 of name './dbtwo/tabletwo.ibd' already exists in the tablespace
InnoDB: memory cache!
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Memory cannot be an issue because the slave is running on a 4 GB box - 303177 K should fit (as they and did before under 5.5.11).

I'd appreciate any help and/or hints, thanks in advance, Christian