unhandled exception Access violation writing location in Visual Studio - c++

Question

Is there a way in Visual Studio 2005 to find out which pointer or variable is causing this access violation? I tried to run in debug mode and break when it happens. By looking at the call stacks, it happens in the end of the function (see below). Could using try/catch be able to find out which pointer it is?
EDIT:
Posting my code:
There is a Qt line edit and a checkbox in my application. Toggling the checkbox would switch the data format in the line edit. Like 3'b111 <==> 3'h7. Below is the callback function that is connected to the checkbox stateChanged signal. The exception happens in the end of function, when destructing local variables.
// switch hex/binary format. 15'h0000 <==> 15'b000000000000000
void switchDataFormat(int checkState) {
QLineEdit* writeRegLE = this->getWriteRegLineEdit();
string oldText = writeRegLE->text().toStdString();
string newText = "";
int maxLength;
string regLengthText = oldText.substr(0, oldText.find('\''));
string regValueText = oldText.substr(oldText.find('\'')+2);
int regLength = this->getRegLength();
if (checkState == Qt::Unchecked) {
// switch to binary format
maxLength = regLengthText.size() + 2 + regLength;
string binaryText;
for (int i = 0; i < regValueText.size(); ++i) {
binaryText += hexToBinary(regValueText[i]);
}
newText = regLengthText + "'b" + binaryText.substr(binaryText.size()-regLength); // trimming leading zeros to fit regLength
}
else {
// switch to hex format
maxLength = regLengthText.size() + 2 + regLength/4 + 1;
newText = regLengthText + "'h";
// zero filling to 4*n bits
if (regLength%4 != 0) regValueText = string(regLength%4,'0') + regValueText;
for (int i = 0; i < regValueText.size(); i+=4) {
newText += binaryToHex(regValueText.substr(i,4));
}
}
writeRegLE->setMaxLength(maxLength);
writeRegLE->setText(QString::fromUtf8(newText.c_str()));
}