I am in no way insinuating that the average user needs to run out and do this, but after 6 months of never being able to connect to Kies via the cable, I was fed up. I had other issues with the phone thinking I was always connected to a cable, and some other things. After finding out that there are a lot of dodgy USB ports with these phones, I realized that all my problems could be linked to this. I bought a port off of ebay and installed it myself, and waalaa!! Every problem solved. I connected to KIES straight away. So all this time I had a crappy USB port.
It was a simple install, and Im glad I did it. It was the only way I was getting Ice Cream Sandwich.
Just troubleshoot your problems very carefully, and I bet some of you can be linked back to this problem. Make sure you search this issue and make sure this could be your problem before you assume this and buy a new port.
Samsung Galaxy SII I9100 mobile from Vodafone (UK Edition) running on the AT&T network in the USA
Currently running NeatRom Lite 4.3 & Jeboo 2.1+ kerenel
Samsung Galaxy Tab 10.1 WiFi only (USA Edition)
*retired* Rooted Motorola Droid X on Verizon