mysql innodb space x did not exist in memory
These messages appear to occur when InnoDB hasn't cached a "tablespace object," for a table, which from what I can tell is an internal structure containing the information about the tablespace (.ibd) file for a table.  Under normal conditions all of these would be cached at server startup (and new ones added when tables are created).  

So, this suggests you've got data dictionary issues (corruption in ibdata1?) but the message does not, itself, appear to be a fatal one.

The message comes from dict_load_table() inside innobase/dict/dict0load.c, in response to a FALSE returned from a call to fil_space_for_table_exists_in_mem() in innobase/include/fil0fil.h.

Comments there:

/*Returns TRUE if a matching tablespace exists in the InnoDB tablespace memory
cache. Note that if we have not done a crash recovery at the database startup,
there may be many tablespaces which are not yet in the memory cache.
@return TRUE if a matching tablespace exists in the memory cache */


This suggests that those messages, while not normal under typical operating conditions, are not entirely unexpected if your server is in the middle of InnoDB crash recovery.

The next thing that happens is that InnoDB tries to open the tablespace files, and since there are no messages in your log indicating that this next step isn't succeeding, it seems safe to conclude that the tablespace (ibd) files are at least accessible and the problem will be elsewhere.

All of this suggests that there will have been previous messages and later messages in the log that will give a better indication of the nature of the problem.