Well, the HP-branded i1 Display Pro is $320...ouch! Maybe you could call HP and ask if a standard i1 DP would work. As I recall, the XL30 differed from the XL20 and 24 in that you could plug the colorimeter directly into the monitor and not need software. This is how the Dreamcolor 27" works. Are you plugging directly into the monitor or the computer using the software? HP specifically states that the software won't work on the 27" Dreamcolor...only on the smaller ones.
My XL20 malfunctioned at the end with the calibrate light staying on. It wouldn't accept NCE 2.0 even though the software worked at that time and OS level. I stopped usinmg it at that time, because it also began showing red-green banding across the screen. Not a big deal for me: I got it on closeout at B&H for $300. I would have been upset had I payed full boat, as you undoubtedly are.