Although they are terribly convenient, I don't like melting soap in the microwave. It heats unevenly, and does not really allow for strict control of temperature (I want all my little soapy molecules dancing to the same music, if you will). That said, I don't think high temps would cause air to be trapped in your soap (assuming you are using a clear base) as a high temp liquid base tends to be thin allowing air to rise to the surface. You say your soap temperature is around 60 degrees c, that should be warm enough for most bases to perform well but you could go as high as 65 degrees (around 150f) and see if that helps.
Remember to mix in your ingredients gently as well, to minimize air in your soap. The same with pouring into molds.
You might also want to try a different base, see if you get different results that way.
Oh, I guess I should mention my two favorite methods for melting soap is a double boiler or a crock pot. I personally prefer the crock pot because with a double boiler if you get any soap in the water you are boiling it can create a waxy residue on surfaces around your boiler. As I write this, I am waiting on 6 lbs of SFIC crystal clear to melt in a crock pot. It usually takes a couple of hours, but I know what temperature it will be at every time.
Best of luck and let us know how you make out