As it turns out, and old SIM card will have a lot of scratches on its pins. Some of the may even be bent inwards or otherwise damaged. I was using my original SIM card back from 2004 when I first became a T-Mobile customer. The SIM card was really in poor shape. I visited a local T-Mobile store after talking to T-Mobile engineering support (not the regular customer service) and requested that my SIM card be replaced. Of course, this was done free of charge. It turns out that the SIM cards are not designed to last more than couple of years and they really should not be taken out of the phone frequently as this damages the pins. Long story short, old SIM cards "leak" power due to bad contacts and increased internal resistance.