Thanks for the additional notes! I've been using the last version of GBPVR for... ever it seems, that it didn't occur to me that earlier versions would react differently.
HD PVR: nPVR 2.6.2 with NEWA 1.34 Std Skin
Intel LGA 1155 H67/i5-2400 SB 3.1GHz with HDMI-out, 8GB PC3-10666, Win7 Ultimate x64, Hauppauge Colossus, 1x1TB SATA, DirecTV HD22, dtvTune.exe Ethernet channel changer
RaspBMC Client: RaspBMC rpi-3.6.11 kernel (based on Frodo 12.2) Std Skin
Raspberry Pi B, MPEG-2 & VC-1 licenses, 8GB class 6 SD, AdaFruit USB WiFi, Flirc USB receiver