I also bought cable at @ 350/-. First I tried USB cable, but could not find any driver for the same. The driver what ever available with me I tried, only LG lite worked , but not LG Link. I have not tried R connect. Then I replaced it with COM port cable and everyting worked well. I have also asked ppl to send me USB driver in case anyone is successfully using it, but not received any response. And as you said don't expect help from Reliance and LG ppl.
You can try proper USB dirver for your cable. For COM port cable there is no problem.
I too have a USB cable, which I'm using just to connect to R-Connect. But can't we get anything like USB to RS232 cable by which we can connect to PC via. both?