Even i am getting the same error

String from method public static String getFieldValue(String, String) in 0 ms
System.StringException: Ending position out of bounds: -1

Anyone who has solveds this problem.Please do reply.

This might help - This works in my dev environment. It looks up the contact based on from email, and creates a task for the contact. It sets the description of the task to body of the email. I send an email to the email service associated with this class, and it set the text as designed.

The test class also works.

global class CreateTaskEmailExample implements Messaging.InboundEmailHandler {

global Messaging.InboundEmailResult handleInboundEmail(Messaging.inboundEmail email,
Messaging.InboundEnvelope env){

// Create an inboundEmailResult object for returning the result of the Apex Email Service
Messaging.InboundEmailResult result = new Messaging.InboundEmailResult();

String myPlainText= '';

// Add the email plain text into the local variable

myPlainText = email.plainTextBody;

// New Task object to be created

Task[] newTask = new Task[0];

// Try to lookup any contacts based on the email from address
Contact [] vCon = [Select Id, Name, Email From Contact Where Email = :email.fromAddress Limit 1];
Id Conid;

If (vCon.size() > 0) {
ConId = vCon[0].Id;
}

// Add a new Task to the contact record we just found above.
newTask.add(new Task(Description = myPlainText,
Priority = 'Normal',
Status = 'Inbound Email',
Subject = email.subject,
IsReminderSet = true,
ReminderDateTime = System.now()+1,
WhoId = ConId));

// Insert the new Task
insert newTask;

//Check creation

Task t = [Select Id, Description from Task where Id = :newTask[0].Id limit 1];
system.debug(t.Description);

// Set the result to true. No need to send an email back to the user
// with an error message

result.success = true;

// Return the result for the Apex Email Service
return result;

}
static testMethod void testEmailMileage() {

// Create a new email and envelope object
Messaging.InboundEmail email = new Messaging.InboundEmail();
Messaging.InboundEnvelope env = new Messaging.InboundEnvelope();

// Create the plainTextBody and fromAddres for the test
email.plainTextBody = 'Here is my plainText body of the email';
email.fromAddress ='rmencke@salesforce.com';

// call the class and test it with the data in the testMethod
CreateTaskEmailExample emailServiceObj = new CreateTaskEmailExample ();
emailServiceObj.handleInboundEmail(email, env );

}
}