Why is my istream going bad after I call getline with it

Question

I am writing code for a coding class, and I am writing a class called MyString which is supposed to be able to store a dynamic char array that acts like a String. However, when writing a read() function that is meant to act like the getline() function, I ran into an error after calling getline() with an istream object. After the call, the istream object was no longer good, and I could not figure out why. Any help/ideas would be appreciated.
Here is the erroring method of the MyString.cpp file:

//Copys contents of in into calling object up to when the deliminator is found in in
void MyString::read(istream& in, char deliminator)
{
    char copyString[MyString::MAX_INPUT_SIZE];
    if (in.good())
    {
        cout << "pre:all good" << endl;
    }
    else
    {
        cout << "pre:all bad" << endl;
    }
    in.getline(copyString, deliminator);
    if (in.good())
    {
        cout << "post:all good" << endl;
    }
    else
    {
        cout << "post:all bad" << endl;
    }
    delete[]theString;
    theString = new char[strlen(copyString) + 1];
    strcpy(theString, copyString);
}

Here is the part of my main function that is calling that my read() method:

cout << endl << "----- now, line by line" << endl;
ifstream in2("mystring.txt");
assert(in2);
while (in2.peek() == '#') {
    in2.ignore(128, '\n');
}
if (in2)
{
    cout << "in2 is good!" << endl;
}
s.read(in2, '\n');
while (in2) {
    cout << "in2 is still good: " << in2.good() << endl;
    cout << "Read string = " << s << endl;
    s.read(in2, '\n');
}
in2.close();

Here is the text file:

# This file has some strings that are used in the string test to check
# reading strings from files. The default overloaded >> of your string 
# class should skip over any leading spaces and read characters into
# the string object, stopping at the first whitespace character (this is
# similar to the behavior of >> on char *).  The read method of the
# string class is a little fancier. It allows client to restrict
# how many characters at max to read and what character to use as 
# delimiter, so you can stop at newline instead of space, for example.
# Reading consumes the delimiting character, so the next read starts 
# after that.
#
The  first  time  we  will
    read individual words, next    
we read whole lines

I tried fidgeting around with my parameter, and changing istream to ifstream, but it did nothing. I added the cout statements to test where the fault code was, and once I found that it was the in.getline() statement that was making the istream go bad, I tried looking up my problem from there. I couldn't find anything on this problem despite someone definitely also running into this before. ny help or ideas would be greatly appreciated.