...after 30 minutes on the phone with T-Mobile, and talking directly with RIM, ths issue was EBKAC!
Apparently, on the 7100t, you must NOT ever take the battery out without turning the device off first. If you do, when you boot it back up you will get the white screen with a constant spinning hour glass. Funny thing is, T-Mobile told me to take the battery out like this...
Anyway, as per RIM, directly, all ok now. I've even tested it, powered a unit on, then off, removed the battery, put the battery back in the device, powered it on, and within 2 minutes it was at the menu screen...
Thank God for that!