import wizard error - "File contains uninterpretable data"

Hi,

I've used the import wizard, xlsread and drag and drop into the workspace window to import my excel spreadsheets many times before. However, for some reason, it's now telling me: "File contains uninterpretable data".

My spreadsheet holds 5 columns X 8192 rows of data - no text.

Does anyone have any clues why it's now giving this error and any way to remedy it?

Thanks