Index Match Error

The formula that I have works when the match is a two digit number, but not for a one digit number. Can anyone think of any reason why?

=IF(ISERROR(INDEX('[Dept Class - FY 2007 Feb.xls]345'!$A$11:$G$2000,MATCH($N$95&$A108,'[Dept Class - FY 2007 Feb.xls]345'!$A$11:$A$2000&'[Dept Class - FY 2007 Feb.xls]345'!$B$11:$B$2000,0),4,1)),0,INDEX('[Dept Class - FY 2007 Feb.xls]345'!$A$11:$G$2000,MATCH($N$95&$A108,'[Dept Class - FY 2007 Feb.xls]345'!$A$11:$A$2000&'[Dept Class - FY 2007 Feb.xls]345'!$B$11:$B$2000,0),4,1))

A B C D
55 8 96 780
55 9 140
55 10 390
55 11 745 2430

The problem is matching on column B, returning column D. $N$95 is 55, and $A108 is the value of column B. This formula will return 2430, but not 780.