ADsOpenObject() returns -2147024882 (0x8007000E) -> OUT_OF_MEMORY

I have a C++ DLL that is used for authentication that gets loaded by a Windows service for every login.

In that DLL I use the Windows ADSI function ADsOpenObject() to get a user object from Active Directory.

HRESULT hr = ADsOpenObject(L"LDAP://rootDSE",
                           L"username",
                           L"password",
                           m_dwADSFlags,
                           IID_IDirectorySearch,
                           (void**)&m_DSSearch);

Generally this works since years. But currently I get the error code

-2147024882 (0x8007000E)

which is OUT_OF_MEMORY. When I restart the service that is using my DLL then it runs fine for weeks but then the errors start occuring.

Now I can't find what is out of memory. The task scheduler looks fine and free memory is plenty.
What can I do to fix that?