Strange New(?) Error Message in Essbase API 11.1.2.1

I have been working with Essbase 11.1.2.1 and am seeing an error message that I don't remember seeing in previous Essbase versions.  The new error message is:

Unknown Error: Not a valid entry

I saw this message a couple of times over the past couple of days when working with Essbase members.  On the first occasion, I was calling the IEssCubeOutline.getDimensions() method and saw this error:

Cannot get child member names. Essbase Error(1013383): Unknown Error: Not a valid entry

I traced this issue to code that inadvertently called IEssCube.clearActive() before calling the IEssCubeOutline.getDimensions() method.  The second instance happened when I called IEssMember.getRelatedMemberNames() on an IEssMember object that was obtained from an IEssMemberSelection object.  In this case, the error number was slightly different:

Cannot get related member names. Essbase Error(1013384): Unknown Error: Not a valid entry

I expected the second exception to occur.  The getRelatedMemberNames() method, which returns an array containing the parent, sibling and first child information, is not available unless you obtain the IEssMember object by querying an IEssCubeOutline object.  I was simply surprised that the error message was the same.

Of course, it is confusing that all member objects are not created equal in Essbase.  It will be a great day when Essbase returns a full IEssMember object regardless of the method used to obtain it.  That being said, I am not holding my breath.