It sounds to me as if you lack attic ventilation... when the insulation
was blown in, it's possible they covered the soffit vents, if you have
soffit vents.
http://www.thisoldhouse.com/toh/know...le/0,16417,194
780,00.html

A ridge vent will also help.
http://www.airvent.com/homeowner/pro...dgeVents.shtml

Light color shingles will help.

The purpose of the roof is to shed water, otherwise it should be as well
ventilated as possible while still keeping critters out.

Once you get the attic ventilated the upstairs temperatures should drop.
If they do not drop significantly then you may need to contact a HVAC
contractor to zone your house.

http://www.dspinspections.com/atticventing.htm
http://www.gaf.com/Content/GAF/RES1/...ventchart.html
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Mac Cool