Macbook Pro (Mid 2010) replacement power supply issue I have a multi macbook/macbook pro household, made up of a 2006 mb, mid 2008 mbp, and mid2010 mbp models.  I recently purchased a new 85 watt power supply and immediately noticed that it would not consistently power or charge my 2010 mbp.  When plugged in, it would charge briefly, then alternate between green and amber every 5 to 10 seconds.  The same power supply worked fine with the older 2006 mb and 2008 mbp.  

I returned this power supply thinking it was bad, and got a replacement, which of course behaves identically to the power supply it replaced.  So, now I'm trying to figure out what is different about my 2010 mbp that would cause this new power supply to not charge correctly.  The odd thing is, my older power supplies, work fine with the 2010 mbp.  

So, there's something with the combination of the new style power supply with my 2010 mbp that is causing problems for charging.

I've tried resetting the SMC on the 2010 mbp, which didn't make any difference with the issue.  Does anyone have any ideas on what might be causing this issue?  Any tips or pointers would be appreciated.
Apparently 3rd time is the charm.   I asked to have this replacement power supply replaced one more time, and the 3rd power supply works fine.  Very odd, but things are operating fine now.