In preparation for the Helios launch (http://www.lineage2.com/helios/) on June 29th, server transfers will be stopped for two weeks. Here's a short timeline:
June 22: Last server transfers are processed, and closure of Server Transfer applications.
July 6: Server Transfer applications open again.
July 13: Server Transfers are processed and function as normal once again.
Important note: If you are transferring with the June 22 maintenance period and your transfer fails, it will not process again until July 13.