Array data type conflicts with std_logic_vector definition.

I would like to use a arrays of standard logic vectors of two different lengths so I declare two new data types.

type tx_vector is array (0 to 14) of std_logic_vector(17 downto 0);

type rx_vector is array (0 to 14) of std_logic_vector(24 downto 0);

I then declare a signal using the tx_vector data type:

signal slave_com_tx_data : tx_vector;

But apparently this definition messes up the std_logic_vector definition? Later on in the code I have this line:

Iq_ref <= signed(std_logic_vector("000" & A_temp(7 downto 0)));

Where "A_temp" is declared as a simple std_logic_vector. The compiler throws these errors:

Error (10327): VHDL error at FCMLctrl.vhdl(868): can't determine definition of operator ""&"" -- found 5 possible definitions

Error (10647): VHDL type inferencing error at FCMLctrl.vhdl(868): type of expression is ambiguous - "rx_vector" or "tx_vector" are two possible matches

Error (10411): VHDL Type Conversion error at FCMLctrl.vhdl(868): can't determine type of object or expression near text or symbol "std_logic_vector"

Why does my declaration change the way simple std_logic_vectors operate?

I am using these libraries

library IEEE;

use IEEE.STD_LOGIC_1164.ALL;

use IEEE.NUMERIC_STD.ALL;

Thank you for any assistance you may be able to provide.