Did you consider the last thing? About the battery which can move a little bit in its place?

I will try to find the post and provide it here, seems the battery was moving just enough to disconnect from the power contact on the phone and neded some adjustment to stay in place It was only on some occasion and the owner was going crazy about this as he tried everything he found as a solution.

EDIT: http://talk.maemo.org/showthread.php?t=79143
This is not the link i was referring about, but it is the same thing. I will continue to search for the other one.

EDIT2: http://talk.maemo.org/showthread.php?t=76179
Another thread similar

EDIT3: http://talk.maemo.org/showthread.php?t=53367
Finally found the thread i was referring to.