Yes, there is a max number of nested IF statements. However, you can work around this by doing something like this:
=IF(Z3=W2,X2,0)+IF(Z3=W3,X3,0)+IF(Z3=W4,X4,0)+IF(Z3=W5,X5,0)+IF(Z3=W6,X6,0)+IF(Z3=W7,X7,0)+IF(Z3=W8,X8,0)+IF(Z3=W9,X9,0)+IF(Z3=W10,X10,0)
HTH

Jason