This is the same problem as in this thread I recently started:
http://forums.olapforums.com/viewtopic.php?f=3&t=1391
so the systems settings remain the same: Server & Client 9.1 SP3, Perspectives with Excel 2003 SP2, English language in both, Client & Server
When a client double-clicks the cube to open the CubeViewer, a message box opens, reading "(ObjectNotFound) <cubename> : Error getting subset properties". You can click it away to catch a glimpse of the CubeViewer opening and closing immediately... You can find the screen-shot attached below, I censored the servername away since I don't know whether I am allowed to show it or not - better to take no risks

As you can see in the screen-shot, the first dimensions drop-down is empty, the first dimension is the company dimension which happens to have a perfectly fine working default subset, at least when opened in SubsetEditor.
In this case I was able to open some Views of this very cube - when I assigned the company-Default subset to title, the same error occured after recalculation. The next biggest subset, "Standard" (German for default, a remainder of old days when clients had a German TM1 version), would work perfectly fine.
My next step would have been to create a subset of the elements contained in Default but not in Standard, check if the subset produces the same error, and then delete elements from it until the new subset won't throw an error. Then I would have known which element is bad, but I don't know what I would have done with this information. Unfortunately some colleague solved the problem by recompiling the dimension via xdi before I could narrow down the error -.-
(saving the Default subset as itself or as A and then Default wouldn't help; there are no alias-attribute rules in elementattributes, tough there are s-element rules)
Sadly I am positive, that the error will be seen soon again ...
Did someone find the root of the problem and eradicate it?
When this error occurs the next time, do you think my approach would help me? What do I do if I find the bad element(s)?
Sorry for the new wall-o'-text and the new topic, but topics having 0 answers are twice as interesting as such having 5 or more, at least to me

Thank you,
Lukas