Quartus II 7.2 & Declaring bus range problem

I've fixed the problem by this:

Setting>Default Parameters>

and then redefine MTU and pkt_len_counter

I don't know why but it is working.

after this I encounter another strange problem:

Error (10531): VHDL Variable Declaration error at Ser.vhd(56): variable declared outside subprogram or process must be a shared variable

why? I've fix this problem by using shared varibale:

 
 
architecture Ser_arch of Ser is 
    signal label_mem    : std_logic_vector((Label_Width-1) downto 0); 
    signal data_mem        : std_logic_vector((MTU-1-32) downto 0); 
    signal counter_mem    : std_logic_vector((Counter_Width-1) downto 0); 
    signal prtc_flag    : std_logic;    -- Packet ready to Combine 
    -- prtc_flag uses as signal and it's just the AND of 4 ports. 
    variable sr            : unsigned((SOF_len+Label_Width+MTU+SOF_len-1) downto 0); 
    variable cnt        : integer; 
    variable tmp        : std_logic_vector((SOF_len+Label_Width+MTU+SOF_len-1) downto 0); 
     
     
    -- =====================function decleration======================= 
    -- crating function to convert the std_logic_vcetor to integer: 
    function TO_INTEGER_stdvect (ARG: std_logic_vector) return NATURAL is 
    constant ARG_LEFT: INTEGER := ARG'LENGTH-1; 
    alias XXARG: std_logic_vector(ARG_LEFT 
    ...... 
    ...... 

Why this is necessary to define the shared values I just use this variable in current architecture...

sth strange...