I'm running into a sort of oddity...

I have a File object representing an .xls workbook. I instantiate a Workbook object from the File object. The workbook has a single spreadsheet. When I try to instantiate a Sheet instance using the Workbook.getSheet() method, my application crashes with "common.AssertionFailed".

Here's my code:

/* Start code */

File file = new File( "workbook.xls" );
Workbook workbook = Workbook.getWorkbook( file );
Sheet sheet = workbook.getSheet( 0 );

/* End code */

The funny thing is, I have an Excel file that does not cause this problem. The other four I've tried cause a crash. A "fresh" .xls file (three sheets, no data in any cells) does not cause a crash, which leads me to believe something about the data in my .xls files is causing the problem. Any ideas?

Thanks