Hi, I am having a weird problem where my MBP won't charge reliably. I will plug in the magnetic part to the computer and it will charge for about 10-20 seconds and then it will stop charging. I can then take it out and plug it back in and it might work for a few minutes and then stop or it might not work. There then was a period of 2 days where the charger wouldn't work at all, so I bought a new 60w power adapter hoping that this was the problem but the problem is still there. I did an SMC reset and it didn't appear to help. Surprisingly, the old charger that didn't work at all is now working but it also has the same 10-20 second problem. What do you think the problem is?