Probably battery contacts. My old POS Nokia did that. Take the battery off and clean everything with the eraser end of a pencil. Don't know about the screen but if brake cleaner worked, hey.
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Andy - Reinstated
Hybrid Forum Moderator
'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.