Several ideas, none of which may answer your question, but here goes:
First, what do you mean by "import"? Answering that may provide some
clues. Do you mean you are placing an Excel file that contains a single
worksheet? Do you mean you are copying a range of cells from an open
Excel file and pasting? What are you doing, exactly?
Second, it's possible that the incoming content is picking up a
paragraph style with an indent that forces the content out of the
available cell space. In my experience, this results in the display of a
red dot in the lower right of the cell, but perhaps that's an indicator
you have turned off (if it's possible to turn it off--I've never
checked). It's also possible the content is picking up a character style
that renders it invisible (such as paper-colored type). Try widening the
columns to see if the data appears. If so, adjust the format.
Third, the data in the Excel file may result from a formula that is
linked to other files or sheets that are not accessible to you after import.
Fourth, the data may exceed the cell width in the Excel sheet on your
system. This would be indicated by the cell being filled with
##########. (This is system-dependent; it may look fine on your client's
system but not on yours, because of the way the presentation layer is
generated in Excel.) If that's the case, I don't know whether or not it
affects how the data is imported. The solution is to widen the column in
the Excel sheet.
That's all I can think of off the top of my head.
Dick