C:\WINDOWS\system32\ntdll.dll, Win32 error 0n2 ?

My computer often issue Don’t Send error message during doing MS Exel. I have openned EXCEL.EXE.hdmp file by Windows Debuger and the cause is:
“Unable to load image C:\WINDOWS\system32\ntdll.dll, Win32 error 0n2
*** WARNING: Unable to verify timestamp for ntdll.dll
*** ERROR: Module load completed but symbols could not be loaded for ntdll.dll
ntdll+0xe514:
7c90e514 c3”.

Anyone know how to fix it??Please