What is interesting/confusing is that the article is for Excel 97.
According to the article, the problem has been fixed in Excel 2000.
the cited article describes 4 requirements:
The Input range of the control is linked to a second worksheet.
-and-
.. You zoom both worksheets to percentages other than 100 percent.
-and-
.. The zoom percentage of the two sheets are not equal.
-and-
.. You move a toolbar over the control, click the control and choose values,
or you alternately select each of the two worksheets.
None of them mention a userform and you don't mention a toolbar. So, while
your problem may be related, it certainly isn't the one described as being
fixed in the article. (not to say it is fixed either - don't know; haven't
tested it).
Just for interest, there were several other articles on xl97 that were
related to the zoom percentage and out of memory errors.