Cold air when overheating!?

Hi guys.  I have a 1997 honda civic lx 1.5 5
speed.  I bought it from a friend and
according to him its always ran hot. But he
drove it across the country twice, just had
to run the heat.  He put a new head gasket
and thermostat in it prior to selling it to me.  
I drove it for a couple of months and it was
fine, then it started blowing cold air instead
of heat and was overheating.  I just had a
new water pump and timing belt put in and
I had them flush it.  Its still overheating and
blowing cold air.  I dont know what to do
from here.  Any help or suggestion are
greatly appreciated.  Thanks in advance!