Excel 2003 Adding Unwanted Brackets [ ] to Sumproduct Formula

I am working in Excel 2003. I am working only within a single workbook.

I am using sumproduct across multiple worksheets (25) to a single summary worksheet.

The formula I am using is as follows:

=SUMPRODUCT(('1:25'!A3:A85=A2)*('1:25'!E3:E85=YES))

Worksheets are simply numbered 1 through 25.

However, when I hit Enter the following formula replaces mine seemingly indicating another workbook called "25" as designated by the addition of the brackets [ ]?

=SUMPRODUCT(('1:[25]25'!A3:A85=A2)*('1:[25]25'!E3:E85=YES))

Why is it doing this and how do I get it to just sum across worksheets 1-25 within the workbook?