This error indicates a problem with Excel spreadsheets. Sometimes they look normal, with a relatively small number of lines, but actually they contain millions of empty cells that still count as data, and that's too much for the converter. Strictly speaking, it's the Excel API that crashed trying to load all these empty cells.
If you open the file and press Ctrl-End, it will jump to the last cell it considers active. In a sample file, that was cell IS65535, which means there where a whooping 17 Million empty cells in total.
This is unfortunately a common problem with Excel, and can be caused by formatting whole rows/columns. See here for a description and fix suggestions by Microsoft::
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