Question: Ambiguous Naming

Gurus...

Any idea why I get the "Parts of the expression are ambiguous. Please select one of the suggested meanings." alert on some of this code, but not other parts? I want them all to be "table assignments" not "function definitions" (per my options in the window). I would really like to not have it keep asking me the question on each run, so is there a way for me to be more specific? Thanks in advance!

Fred

deq(i,XMethanol):=M*diff(X[i](t),t)=(L*(X[i-1](t)-X[i](t))+V*(Y[i+1](t)-Y[i](t)));

deq(i,XWater):=XW[i](t)=1-X[i](t);

deq(i,YMethanol):=Y[i](t)=(X[i](t)*PP[M,i]*GAMM[i])/(Pbar);

deq(i,YWater):=YW[i](t)=1-Y[i](t);

PP[M,i]:=exp(CM+DM/((T[i](t)+273)));

PP[W,i]:=exp(CW+(DW)/((T[i](t)+273)));

GAMM[i]:=exp((A*XW[i](t)^(2))/(((XW[i](t)+(A*X[i](t))/(B))^(2))));

GAMW[i] :=exp((B*X[i](t)^(2))/(((X[i](t)+(B*XW[i](t))/(A))^(2))));

PCalc[i]:=XW[i](t)*PP[W,i]*GAMW[i]+X[i](t)*PP[M,i]*GAMW[i];

deq(i,Temp):=Pbar-PCalc[i]=0;