Assuming that you have tried removing the battery for a few minutes before trying it out again and nothing had changed then there isnt really anything more "externally" you can do.

There is of course an internal memory back up button cell battery but this usually requires an element of rear case dismantling to access it.

When you refer to not being able to use it since connecting the DVi connector, if you are meaning that it stopped working from that point onwards then whatever you connected into it should be suspected of possibly causing the problem, so it would be interesting to know what it was?

Of course in the past quite a number of people with somewhat lesser spec JVC devices experienced failures of the same nature as yourself after having plugged whatever into their camcorders DVi sockets, and was a problem that was never completely satisfactorily resolved because of the variables involved regarding what could cause the problem. (i.e:- external as well as internal)