PC does not detect tablet

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http://forums.androidcentral.com – I've connected my tablet to my PC (with Kies installed in it) thru USB, but the pc doesn't recognize it. I tried plugging the tablet to another PC (without Kies), and it didn't detect the tablet either. Two days ago, it was still working well, as i have been able to transfer files between them. Note: USB Debugging is already checked; no updates have been made in the past few days. I don't think there's anything wrong with the usb cable i'm using, because: • in the PC (windows 7) where Kies is installed, everytime i plug the tablet in, a notification balloon appears saying installation of (HowTos)