Excel 2003 max lines circa 65,000
Excel 2007 max lines circa 1,000,000
If you're opening a file which was created in 2003 or earlier, then you will still be limited to 65536 rows. To increase this you need to convert it to 2007, you’ll then get over the 65,000 barrier
Make sure the file type drop down
doesn't say ".xls", but says ".xlsx" or ".xlsm" etc.
Hope this helps