I actually had exactly the same issue you are mentioning. Yesterday my PLM decided to stop working. Went to the local electronics place and picked up some capacitors to replace the ones on the board. $5 and about an hour of time and the PLM is back in business controlling the lights again. If you can solder and have the equipment it is usually an easy fix to get it going again.
That said, I have been thinking of upgrading to Eisy ISY with a USB PLM and using my current setup as a backup - I just have too many devices to risk losing control.