How do I fix Replication event checksum verification failed while reading from network. Error_code: 1743
Try resetting the relay logs as follows:
STOP SLAVE;
CHANGE MASTER TO master_log_file='mysql-bin.000030',master_log_pos=196820914;
START SLAVE;

This will erase all relay logs in the Slave, starting with a fresh one. It should start retrieving binlog events from the Master. If it fails again, then mysql-bin.000030 on the Master may be corrupt. In that event, you would have to set up replication from scratch by doing this:

Stop the DB Application
On the Master, RESET MASTER;
mysqldump the data from the Master
Load the mysqldump on the Slave
On the Slave, run STOP SLAVE;
On the Slave, run CHANGE MASTER TO master_log_file='mysql-bin.000001',master_log_pos=4;
On the Slave, run START SLAVE;

CAVEAT
Make sure the network connection is clear (with no dropped packets) between Master and Slave.
Give it a Try !!!