(HW) Pallindrom using Stack and Queue, Run Time Error - stack

Question

Alright, i have a hw assignment to check if an inserted string is a palindrome. The string must first be inserted into a stack, a queue, and then compared. I have the program up and running, for me that is. My teacher, when trying to grade it experience(d) a run time error. Also, getline portable is a requirement of the assignment and came with the file and instructions.
This is the note from the teacher:
Check if a line is a palindrome. Ignore spaces? y/n y (her running the code)
Input line to check
(where she gets the runtime error)
175 [main] csc240Summer2014PE8Student 10060 open_stackdumpfile: Dumping stack trace to csc240Summer2014PE8Student.exe.stackdump
#include <iostream>
#include <stack>
#include <queue>
#include <string>
using namespace std;
istream& getline_portable( istream& is, string& str ) {
istream& ris = std::getline(is,str);
if ( str.size() && str[str.size()-1] == '\r' )
str.resize(str.size()-1);
return ris;
}
int main()
{
stack<char> s;
queue<char> q;
char c, choice, b;
string str;
int i = 0;
int count = 0;
do
{
cout<<"Check if a line is a palindrome. Ignore spaces? y/n ";
cin >> b;
cin.ignore();
tolower(b);
cout<<"Input line to check\n";
getline_portable(cin,str);
for(int j = 0; j < str.size(); j++)
str[j] = tolower(str[j]);
if(b == 'n')
{
for(int j = 0; j < str.size(); j++)
{
c = str[j];
q.push(c);
s.push(c);
}
}
else if (b == 'y')
{
for(int j = 0; j < str.size() - count; j++)
{
c = str[j];
if(isspace(c))
{
}
else if(!isspace(c))
{
q.push(c);
s.push(c);
}
}
}
do
{
if(q.front() != s.top())
{
i = false;
break;
}
else
{
i = true;
s.pop();
q.pop();
}
}while(!q.empty() && !s.empty());
if (i == true)
cout << str << " is a pallindrom.\n";
else if (i == false)
cout << "Your input of " << str << " is not a pallindrome.\n";
cout << "Would you like to test another string? y/n ";
cin >> choice;
tolower(choice);
cin.ignore();
}while (choice == 'y');
cout << "Press enter to continue...";
cin.get();
return 0;
}