More information is needed.
*What cabling pin-outs are used?
*What are you connecting to the serial port and is it DCD sensitive?
*What port profile is used?
*What flow control method is used?
*What port signals are seen as active during the connection and during the re-connection (this can be displayed under the web interface: Device Information > Serial Ports & Diagnostics)?
*Is the RealPort driver being used? If so, what operating system and version?