It seems you have a deserialization problem. The stack says that it is trying to read an unsigned short from your AMF and it can't as the stream has no more bytes to read. (basically trying to read more data from AMF than it contains) Your java classes and your AS3 classes are not synchronised. Did you modify your java classes and forgot to regenerate your AS3 files with the granite plugin (or maven plugin)? Adding a field on the java side without regenerating could be the reason.
Granite serialization system is based on IExternalizable on AS3 side: it is explicit (a huge difference with BlazeDS which can adapt data at runtime and can convert type fields for instance at runtime).
Check your generation of AS3 files and eventually the granite server configuration.