program break help!!

[amir10z]

in the program i built from a "students.txt" file a binary tree. and from each students i make a new linked list the the grades that i took from "grades.txt" file.
the code i put here is the code for the 2 functions that build the grades list from the "grades.txt" file, the programs runs but break in the while loop. i dont know why?? help please, thanks!! if you want to see the whole code you can enter: C | // -----------------------------------------------

the students.txt file is build from:
id number - 9 chars
first name - 26 chars
last name - 26 chars
space between each field.

the grades.txt file is build from:
id number - 9 chars
grade - int
exercise - int
space between each field.

2 functions code, the second calls the first, the break happen in the second in the while loop:

// ----------------------------------------------------
//	Synopsis: Recursively insert student grades to tree.
//
//	Arguments: 
//		- Grades file name
//		- pointer for tree root
//
//	Return-Value: FALSE on failure. TRUE otherwise 
// ----------------------------------------------------
int InsertGradesTreeNode(StudentNode * proot, GradeNode * newGrade, char id[ID_SIZE])
{
	StudentNode * root;
	GradeNode *nextNode = proot->student.gradeList; 
	int cmpResult;

	if (proot == NULL)
		return FALSE;

	root = proot; // Used just of cosmetics
	
	cmpResult = CompareId(id, root->student.Id);

	if (cmpResult == 0)
	{
		for (; nextNode->next != NULL; nextNode = nextNode->next);

		nextNode->next = newGrade;
		return TRUE;
	}
	
	// Advance right of left, based on compare
	if (cmpResult > 0)
	{
		return InsertGradesTreeNode(root->right, nextNode, id);
	}		

	if (cmpResult < 0)
	{
		return InsertGradesTreeNode(root->left, nextNode, id);
	}

	return TRUE;	
}



// ----------------------------------------------------
//	Synopsis: Load student grade list to appropriate
//			student node.
//
//	Arguments: 
//		- grades file name
//		- pointer for tree root
//
//	Return-Value: FALSE on failure. TRUE otherwise 
// ----------------------------------------------------
int LoadGradesFromFile(const char * filename, StudentNode * proot)
{
		
	GradeNode gradeN;
	FILE * gradesFile;
	char id[ID_SIZE];
	
	// Zero gradeN in advance
	gradeN.next = NULL;
	gradeN.grade.grade = 0;
	gradeN.grade.exercise = 0;
		
	// Open grades file
	gradesFile = fopen(filename, "r");
	if (gradesFile == NULL)
	{
		fprintf(stderr, "fopen(%s) failed\n", filename);
		return FALSE;
	}
		
	// Add each student grades in file into tree
	while (EOF != fscanf(gradesFile, "%9s %d %d", id, gradeN.grade.grade, gradeN.grade.exercise))
	{
		if (!InsertGradesTreeNode(proot, &gradeN, id))
		{
			fprintf(stderr, "CreateGradeReport failed!\n");
			fclose(gradesFile);
			return FALSE;
		}
	}

	// close and exit
	fclose(gradesFile);

	return TRUE;
}

[tabstop]

If you're going to make a tree out of this, you have to give every student their own node (i.e. via malloc), and not keep reusing the same piece of memory over and over and over again/