Using MySQL server 5.1.47-community-log, I kept getting errors when installing the module, about an error in the MySQL syntax near "primary key", for both tables. Only ljsync table was created.

In the end I changed, in ljsync.install 'unique keys' to 'unique key' in the two tables' instructions, I didn't get the errors and the tables were created. However, I really have no knowledge of MySQL, so right now I don't know whether I've fixed the problem for me or just made it set fewer unique keys.. or something similar.