Actually the clustered\ nonclustered bit is not mandatory. I just like to put it in so it is explicit. It also appears that there was a copy and paste problem (apologies) - there should be a space between nonclustered and index. The difference was actually as mcrowley said - you "qualified" the index name when you should not have.
A pk and a not null unique index are exactly the same as far as sql server is concerned.