I'll 'assume' you are using the HDMI outputs from the HR34 to your display, have you thought about checking the component outputs (which is what the Hauppague uses) as well?
I've seen lots (okay, more than a half dozen) 'newer' DirecTV dvr's as of late (mostly HR24's) that the component outs don't work; apparently, it isn't in the final (or earlier) checklist in manufacturing 'tests', if any.
Lots of folks never think to 'check' those as they simply plug up the HDMI and go. Big mistake. Same with never checking the SPDIF/optical audio outs.
Do it. I think you'll find that they don't work. Either that or your cables and/or the HD-PVR stopped working for some reason.