wrote on Jun 30^th, 2012 at 4:16pm:

I have had success with the PDCS calculating the CRZ speed. Try this and see if it works for you  :) I enter this info before T/O on the TEMP 2-2 page (I don't enter during climb or cruise because FSX will often CTD): Enter anticipated FL [320] (you can use the V-One OPT Alt & add about 4,000 ft, e.g. 316 + 4 = 320) Enter SAT °C [-48] (see below for FL & temp values) Enter ISA °C [0] When at desired altitude, set selector switch to CRZ, and update WIND to [0]. I've tried different entry sequences into the PDCS and never had the CRZ speed calculate correctly on the ground.

Thought I should give an update:

Before my last flight I entered the airport field temp and ZFW in the load page...no other data was entered...anywhere.
After reaching cruise alt, I turned the control knob to CRZ and then pressed 'RCL'.

The CRZ EPR was properly calculated (.720), apparently any other input has no influence whatsoever  :(