We have noticed that we have seen a variety of Macs, primarily running 10.4.10 and higher, and particularly Macs with Intel chips that are having difficulty connecting to their i1 devices. These devices will show on the USB chain when viewed in System Profiler on the Mac, but will not be seen by i1Diagnostics. They will show as "device not found".
Some HP printer drivers seeom to have unexpected impacts on USB and possibly FireWire devices that previously worked without issue. This issue can be resolved by uninstalling your HP drivers and loading updated drivers from Apple, or by connecting your HP printer and running Software Update. These drivers require Mac OS 10.5.3 or greater.