Array indexing problem: "Data corruption (ListDelShift) - Bad Index"

Hi,

I'm trying to access a single element of a std_logic_vector, and I am
getting this error from ISE (6.3i):

"FATAL_ERROR:Xst:listutil.c:503:1.19 - Data corruption (ListDelShift) -
Bad Index Process will terminate. To resolve this error, please
consult the Answers Database and other online resources at
http://support.xilinx.com. If you need further assistance, please open
a Webcase by clicking on the "WebCase" link at
http://support.xilinx.com";

The code that generates this is:

process(output_enable)
variable temp_weight :
std_logic_vector(weight_precision - 1 downto 0);
begin
if config_enable='0' then
for i in weight_precision - 1 downto 0 loop
temp_weight(i) := weight_table(0); <== ERROR HERE
end loop;

weight <= SXT(temp_weight, adder_input_width);
end if;
end process;

The error would appear to refer to the "weight_table(0)" statement.
Normally, I don't reference just the 0'th element - I use an expression
to calculate the bit I need - but the error still occurs. The error
occurs with other indices (such as 1,2,3 etc, and also
"weight_table'length - 1") too.

weight_table is defined as:
"signal weight_table : std_logic_vector(weight_table_left downto 0)"
where "weight_table_left" is 63 in this case.

"weight_table" is initialised to all zeros.

I'm sure it is something simple, but I just can't see it. Can anyone
help?

Many thanks,
Robin

.

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