If you want to use the serial terminal over LemonIDE, first you need to copy the files "rxtxParallel.dll" and "rxtxSerial.dll" into the System32 folder of XP. Second, you must copy the file "RXTXcomm.jar" into the java folder, for example "C:\Programme\Java\jre6\lib\ext". Then please restart LemonIDE.
For more information please visit
http://www.eldesi.com/wiki/Using_the_serial_terminal_of_LemonIDE