Problem with new D5100 found..

As you want to use it with manual lenses, it seems you got the better camera anyway. You got a bigger and better focus screen and the rangefinder on the D7000 is 'reported' to work even better than the D300 one, for manual focus.

I get my D5000 focused ok in manual, but I am going to upgrade for a bigger focus screen and updated sensor at some point. The D7000 or its replacement  (or the D700 used) will be options.

Seems like the best choice for you at this time.

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.....Just from an amateur......''Sometimes it's to your advantage for people to think you're crazy.”