Hi Dave,
More details will help
What software are you using. Like if its Vixen do you have the Add-ins DMX checkbox checked if so than the lynx dongle won't work (it needs to be unchecked)
So Software, Do you have more than one dmx controller?, What firmware was loaded unto the pic, Have you tried different cat 5 cables, Does the LE test work, did you load the FTDI drivers, does the computer "see" the dongle, Are the parts in the correct location and in the correct orientation, Is the crystal the right frequency, and of course quality pictures of the dongle front and back
Rick R.