Roo gem performance problems

I am getting unacceptable performace problems by using the roo gem for
reading a file by using XLSX or XLS library from this gem.

Someone may suggest me an alternative about how to parse an .XLSX file?

<code>
parsed_file = Excel.new(filename,false, :ignore) if (file_format.upcase
== "XLS")
      parsed_file = Excelx.new(filename,false, :ignore) if
(file_format.upcase == "XLSX")
      raise t "#{filename} is not an Excel file!" if (!parsed_file)

      parsed_file.default_sheet =
parsed_file.sheets[0]#'Sheet2'#oo.sheets[1]

      first_row = parsed_file.first_row
      last_row = parsed_file.last_row
      first_column = parsed_file.first_column
      last_column = parsed_file.last_column
      #logger.info "#### Total Rows:#{last_row}, first_row:#{first_row},
last_row:#{last_row}, first_column:#{first_column},
last_column:#{last_column}"

      first_row.upto(last_row) do |current_line|
              # Stuff ....
      end
</code>

Thanks

More details

http://stackoverflow.com/questions/4875188/roo-gem-xlsx-files-performance-problems/4887273#4887273