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Did you SSH into the phone and change the SMS rings? Or, when you restored to 4.1 did you restore from an iPhone backup? You may need to restore again and set up as new iPhone. The jailbreak files can carry through a restore if you choose a previous iPhone configuration.
 
what is this 'electricity" tone you speak of?

pick another tone and then turn the sms sound off to see what happens..
did you modified SMS tones?
 
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