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

Technote (FAQ)


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.

Document information

More support for: Lotus End of Support Products
Lotus Notes

Software version: 6.0, 6.5

Operating system(s): Linux, Windows

Software edition: All Editions

Reference #: 1224056

Modified date: 20 November 2009

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