just a guess - but are you bringing the PLC-5's data in and then storing it in a DINT location? ... if so, that MIGHT be your problem ...
the PLC-5 thinks in terms of INT locations (16 bits to each location) ... the ControlLogix NORMALLY thinks in terms of DINTs (32 bits to each location) ...
try setting up the ControlLogix storage locations as 16-bit INTs and see if that helps ... if not, consider posting your program file (ACD) and we'll try to help you nail down an answer ...