problem while I was in the loop?

FILE *fp;
fp = fopen(ImeFajla->Text.c_str(),"a+");
if (fp == NULL)
    Label1->Caption="Neuspjesno ovaranje fajla...";
Label1->Caption="Ucitan sadrzaj fajla";
char s[101];
while(fgets(s,100,fp) != NULL)         
// *problem Project Project11.exe raised exception class EAccessViolation 
// with message 'Access violation at address 3286ED28 in module 
// 'CC3280MT.DLL'. Read of address F85BE2DC'.
{
    ListBox1->Items->Add(s);
    n++;
}
fclose(fp);
}