Cvx Disciplined convex programming error

Hi. i have problem in cvx.
variable is qpnew.
the error is:
Error using + (line 83)
Disciplined convex programming error:
Illegal operation: {real constant} + {log-concave}

Error in tra1 (line 61)
rs2(1,i)=.5*log(1+(pS(1,i)*B0/NS)exp(-2norm(qpnew(:,i)-ws)))*t;
i dont know what is real constant in this .please say me what should i do with this error.

Better to give more details.