DVI to mini DP converter(s) not working

does anyone have any good information on why an older Belkin and now a newer Kanak "DVI to Mini Display Port" converter would not be working? i have a 2006 mac pro with a DVI port and the computer WORKS when i hook it up to a DVI compatible monitor but it doesn't work when i try to hook it up to the cinema display with a DVI to Mini Display port cable.

the BELKIN used to work and then i had to buy a new one because i thought it broke when i wasn't getting a display on my cinema display.

i know the monitor works because i can hook it up to my 2012 mac pro that has mini DP ports. and again i know the video card and the 2006 computer work because i can hook them up to a DVI compatible monitor.

thanks for any help.