Then you are using the SLC"s serial port, right?
Do you know how your SLC5/03 serial port is configured?
For the 1747-UIC to work your SLC5/03's serial port would have to be configured for DH485, is it?
Do you have the offline file? If so check the serial ports configuration or post your .RSS file and someone here can take a look. Zip the file first then post.
If the port is configured for DF1 then you need a USB to serial adapter, if you don't have a real serial port on your PC. A "keyspan" is a good one.
If your PC has a real serial port then the cable 1747-CP3 should work for DF1 protocol. ( use RSLinx's RS232 DF1 Devices Driver for DF1 protocol)
See link below if you need one( scroll down right hand side)
http://www.plctrainer.net/
What port was the Panelview connected to and again what is the complete catalog number of your PV? This info may help us determine how the SLC5/03's serial port is configured.
See PDF below for how-to connect to your SLC's serial port if its configured for DF1 protocol.