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Error: 'An error was encountered while opening a window' when launching Notes

Question & Answer


If you quit or exit Lotus Notes® normally, sometimes the nnotesmm.exe or ntaskldr.exe files are left in memory. This prevents Notes from launching on the next attempt with the following error message:

    "An error was encountered while opening a window."
This error occurs far more frequently if you quit or exit Notes prematurely or abnormally.


The Notes code is consistently unloading nnotesmm.exe. Ntaskldr.exe should unload as expected although it may stay loaded if Notes has crashed.


The issue involving the unloading of nnotesmm.exe was reported to Quality Engineering as SPR# HNAA6E89C5 and was addressed in Notes/Domino 6.5.6.

If the ntaskldr.exe is not unloaded as expected, use the operating system's Task Manager to end the process (press CTRL+ALT+DEL --> Task Manager --> select ntaskldr.exe --> End Process --> close Task Manager).

Fix details: SPR# HNAA6E89C5

Refer to the Upgrade Central site for details on upgrading Notes/Domino.

If you haven't yet upgraded and experience this situation, contact Product Support to see if a hotfix is available for your particular configuration.
NOTE: Occasionally, anti-virus software monitors database access by using NSF_HOOKS or EXT_MGR. Usually, these process are launched as Windows Services so when these processes hold memory, you cannot launch the Notes client even if you log out of your Windows account. You must restart the operating system or service application using the net stop/net start command or services.msc.

Nnotesmm.exe monitors shared memory usage (the number of OSInitRefCount) so that unaccessed shared memory is not released by the operating system. Premature shutdown sometimes fails to decrease the counter so nnotesmm.exe falls into an infinite loop which causes the error above.

Internal Use Only

NOTE TO SWEs: From an Update to this technote: "I do have a customer that is experiencing this issue in Notes 8..0.2. The end user did have a crash,and the ntaskdlr executable was still running. The end user tried to reopen Notes and was prohibited from doing so. Ending this task allowed the user to restart Notes. At this time, they are not able to reproduce the issue on that user's workstation but I have asked them to enable some debug parameters in case it does happen again."

HNAA6E89C5Notes SPRs

APAR LO09093
APAR LO09118

Contributors: Richard C Fucarile, Matt Garoian, Vivek Ashar

If you quit or exit Lotus Notes normally, sometimes the nnotesmm.exe or ntaskldr.exe files are left in memory. This prevents Notes from launching on the next attempt with an associated error message. Why does this happen?

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Document Information

Modified date:
16 June 2018