Just a quick note on some issues I had debugging a MonoDroid app I've been playing with (MonoDroid is very cool, BTW)... for some reason I couldn't get a Samsumg Galaxy Tab to be recognised as a USB device when connected to my 64-bit Windows 7 PC.
Googling turned up a few different 'ideas' like Samsung Galaxy S Problems, Samsung Kies Software and PC connectivity and Connect Samsung Galaxy S with Kies on your PC - The MTP Error. None of those suggestions worked for me, despite a lot of mucking about with driver installs.
It turned out a hint in this post on USB connection trouble fixed my problem... "somehow" the device's USB port was set to 'modem mode' and I had to type *#7284# on the phone keypad to re-set it! Un-in-tuitive!
The Kies Samsung software/drivers off the Samsung website were fine, once the device was in 'USB mode'.
Anyway, hope that helps someone else...