No logic elements although I have an output

The problem I got after removing for statement is that , I have a shared signal which is a 2D array. I assigned values to different cells in each process. But in compilation, Multiple constant assignent error is shown . My question is that , Isn't it possible to assign values to the same array in different processes if the places of assignment are different ?

This is the code if you may...

-- In process 1 :

if (clk' event and clk='1') then

Bufftemp(2*j,2*i+1)<= Im(2*j,2*i+1) - 5;

end if;

-- In process 2 :

if (clk' event and clk='1') then

Bufftemp(2*j,2*i)<= Im(2*j,2*i) - 5;

end if;

Error : Error (10028): Can't resolve multiple constant drivers for net "Bufftemp[0][0][9]"