Line of code not translating from 2003 to 2007

Hi there, I am trying to run a macro created in excel 2003 on my 2007 machine.

I don't know vba unfortunately and when I try to run a macro, I get the debugger. There is no issue with the Macro using xl2003.

The line of code it highlights, is the following.

LastRow = Master_Wksht.Range("N" & Rows.Count).End(xlUp).Row

Is there any immediate reason why this line might fail?

Thank you for your time.