I would say its a model fault, try the other parts in the same family.
I try Other parts LPC1311 and it reports the same error.
with just the device the good ones complain of no program code, so passing the device pin test.
I Created a new schematic design and then try to place LPC1343 and tries to run the simulation, hoping that i will get Program Not Specified Error, but i get the Same error as described in my first post.
Does anyone had installed Proteus 8.1 in his system, please check whether the device is working on your system or not.
This video shows that LPC1343 Run's in Proteushttps://www.youtube.com/watch?v=pkgwvAMLXoU
This guy is using Proteus 7.10, i think he copies the files Model and Libraries files from Proteus 8.1.
This video shows that LPC1343 works in proteus.