Last month, Canon updated the firmware in its WFT-E1/E1A transmitter to v2.0.1.
The firmware release enables the unit to work with the EOS 20D. It also fixes a bug involving the WFT-E1/E1A's file overwrite settings:
"If you try to make a new file when [No] is selected with [Overwrite Same File] in the FTP server setting, the WFT-E1/E1A used to show [Err99] on its LCD and stop working. This problem has been settled in this updated firmware."