Passing Substitution Parameters to run_Batch_Job Web Service

I've been struggling with setting global variables and substitution parameters for my batch job submitted through the Web Service. I have a simple job with a script that refers to one global variable and one substitution parameter.

Job_param_typeSubstitutionParametersParameter[] parms =

          new Job_param_typeSubstitutionParametersParameter[1];     

parms[0] = new Job_param_typeSubstitutionParametersParameter();

parms[0].setName("$XXX");

parms[0].set_value("Test");

jobParameters.setSubstitutionParameters(parms);

request.setJobParameters(jobParameters);

RunBatchJobRequestGlobalVariablesVariable[] globals =

               new RunBatchJobRequestGlobalVariablesVariable[1];

globals[0] = new RunBatchJobRequestGlobalVariablesVariable();

globals[0].setName("$$YYY");

globals[0].set_value("Test2");

request.setGlobalVariables(globals);

When I pass this request to run_Batch_Job, that call times out after about 5 minutes with a socket read timeout. If I don't set the globals or substitution parameters, the call completes, and the job runs fine.

The script in the job looks like the following:

print('Global: ' || $XXX);

print('SubParm: ' || [$$YYY]);

What might I be doing wrong?