There is one other issue that can cause the fault state that you have described. On all of the ipod touch logic boards (brain of the ipod) the data in / out lines have a dual fuse attached in-line. Normally only one half of this fuse block goes dead but that is enough for the ipod to not be detected by your pc or mac and it will definitely stop it from charging.
I own and run my own business in Australia and we repair this fault all the time.
To fix this problem you have to be very steady with a good fine tipped soldering iron and have great eye sight or a good magnifier. As long as only one side of the fuse block is dead then you can safely by pass it with a single filament of thin wire. Please note when testing the block, test from the dock socket side to the direct opposite. Not across the dock socket.
The fuse block can be found, when looking at the ipod with the dock socket closest to you, just above and to the right. the block is about 2.5-3.5mm square with 4 metal legs, the tops are exposed for easy testing, (look like silver dots on the top of the block).
Hope this helps.
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