Segmentation Fault

I'm getting a run-time error flagged by GDB which says:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 3412.0x4ac]
0x7c96df51 in ntdll!RtlpNtMakeTemporaryKey ()
from C:\WINDOWS\system32\ntdll.dll

My program is running well if I'm not using debugger to run it. What could be the cause of this error? And why is my app not crashing if I'm having a segmentation fault?

What does 'backtrace' says?

backtrace says:

#0 0x7c96df51 in ntdll!RtlpNtMakeTemporaryKey()
from C:\WINDOWS\system32\ntdll.dll
#1 0x7c94a5d0 in ntdll!RtlInsertElementGenericTableAvl()
from C:\WINDOWS\system32\ntdll.dll
#2 0X7c9268ad in ntdll!iswdigit () from C:\WINDOWS\system32\ntdll.dll
#3 0x77c2c2de in msvcrt!free() from C:\WINDOWS\system32\msvcrt.dll
#4 0x052b0000 in ?? ()
#5 0x00000000 in ?? ()