Can't find Layer ID (26::93)

Hi,

I've got a CS6 project file that opens fine on some machines but on others i get the error "(26::93) Can't find layer ID=3173 in composition". There are about 10 missing layers, they're not unlinked or anything they're simply not in the project, but they are when i open it on other machines. All the versions of OSX are the same (snow leopard), and all the versions of CS6 are identical.

There's no reference error list i can find for after effects which seems rediculous to me as the error codes are useless without one.

Any ideas?