Maybe "archer" is into something about the size of the package. I have experienced that there are two things that can make a package too big for Oracle to handle. The one thing, as archer has stated, is size. The other thing is the actual number of package variables, constants, types, methods etc. (private and public). If this number becomes too large, it can also inflict on how well Oracle can compile and debug the package.
"serelay", can you please tell us the number of public (package header) and private (package body) variables, constants, types, functions, procedures etc. your package have, respectively. Also, what types of parameters are your package methods typically called with (type of parameters, number of parameters, function/procedure, number of in, out, and in/out parameters etc.)