Error 121 is a foreign key constraint issue. The first thing to check is that your foreign key definitions are ok (all the tables and field names are correct, etc.).
You can try disabling foreign key checks before creating the table as well, like this:
SET FOREIGN_KEY_CHECKS = 0;
That has the downside of throwing errors later when you re-enable your key checks (set it to 1), however, if this is the case, then it means you have some invalid records somewhere that are interfering with the creation of the foreign key.
However, this issue can also occur if you've been manually moving database files around, such as physically renaming the
data/your_database_name directory. InnoDB can't correlate physical changes like that to the tablespace, so it mucks with the internals.
If this is what you did, the solution that works best is to move your old database back to where it was, take a dump or export of it, and do a
DROP DATABASE on it before re-importing.