Thanks for all the input. I should clarify that I replaced the rear tires with the identical brand & size tires as before.
Sorry, I stated the incorrect profile for the fronts... they are actually:
Front - 18x8.5 +38 with 225/
40 tires
Rear - 18x9.5 +38 with 245/35 tires
(corrected original post)
These tires are Max Performance Summer Tires:
http://www.tirerack.com/tires/tires....remeContact+DW
Since I've double checked everything, I'm crossing my fingers that it just has a very long break-in period before the new tires start gripping like the worn-in fronts do. Maybe it's time to start doing burnouts!