Found answer to loose cable
I've posted elsewhere about my KT being a lemon, after having this problem of the loose cable (at the KT end of the cable). After several email interchanges with Kobo customer service, I sent my KT back to be repaired (Chapters/Indigo doesn't take back Kobo's; Chapters advises KT owners to send their ereaders back to the address given by Kobo customer service). The repair people connected my Kobo to a PC and a Mac, with no problems - and sent it back to me. I wasn't happy about it, but what are you going to do when the manufacturer says everything is A-OK?
Anyways, when I got it back, I decided to try a couple of things on my own. I purchased a new USB cable, which seems to have helped somewhat. On several occasions (prior to sending it back to Kobo), my computer kicked out my KT, saying that it had been disconnected improperly, rather than being ejected (I hava MacBook Pro). So, I tried this: keep the device on a flat surface and don't move it at all during the time it is connected to my computer. I haven't had a problem since. Maybe this will work for other people with this loose cable problem?