Sometimes the client times out when importing large DBs. That goes for all clients (if the file is really large). I always import the sql files manually through the terminal/command prompt.
1. Login into mysql: mysql -u <username> -p <password>
2. Import the database manually.
Example: If you need to import to the characters database
At the mysql prompt type
use characters; source <path_to_your_file>\largefile.sql;
Import to world
use world; source <path_to_your_file>\largefile.sql;