Once the virtual comport driver is installed, try plugging in the USB programmer board to the computer. The virtual COM port should show up in the /dev directory, where all hardware device files reside on a Unix system. The virtual COM port is named staring with ttyUSB. To see that it showed up, try listing everything that starts with ttyUSB in the /dev directory:
$ ls /dev/ttyUSB* /dev/ttyUSB1
In this case the port is named ttyUSB1, but it might also be ttyUSB0. Now we are ready to run the flash utility.
There is a very nice flash utility for programming the LPC2000 series ARM processors under linux called lpc2k_pgm. It is available here. It has a convinient graphical interface, and is easy to use.
Connect the Critter Board to a power supply, and then connect the USB programer baord as in the picture. There are two slide switches on the USB programmer board to select run and program modes. When the switches are in the program mode (towards the USB connector), the computer has the ability to reset the LPC2138 into bootloader mode. Make sure the switches are in the program position.
When you run the flash utility, you will need to specify the the serial port (from above) and the .hex file to upload. The crystal on the Critter Board is 14.7456 MHz, and the baud rate can be set to 115200 for a quick upload.