Ed, maybe this log can help you track this issue. They are the relevant messages received since I turned the UR on (keep in mind it is not working as an audio device).
26/04/12 11:41:04,232 Kontakt 4: Error loading /Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio: dlopen(/Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio, 262): no suitable image found. Did find:
/Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio: no matching architecture in universal wrapper
26/04/12 11:41:04,232 Kontakt 4: Cannot find function pointer NewPlugIn for factory C5A4CE5B-0BB8-11D8-9D75-0003939615B6 in CFBundle/CFPlugIn 0x101edc820 </Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin> (bundle, not loaded)
26/04/12 11:41:04,233 Kontakt 4: Error loading /Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere: dlopen(/Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere, 262): no suitable image found. Did find:
/Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere: no matching architecture in universal wrapper
26/04/12 11:41:04,233 Kontakt 4: Cannot find function pointer New_SHP_PlugIn for factory 834FC054-C1CC-11D6-BD01-00039315CD46 in CFBundle/CFPlugIn 0x101edc8b0 </Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin> (bundle, not loaded)
26/04/12 11:42:22,216 [0x0-0x313313].com.native-instruments.Kontakt 4: Latency (Input: 1, Samplerate: 16000) device: 16, stream: 0, securityoffset: 21, buffer: 512, total: 549
26/04/12 11:42:22,216 [0x0-0x313313].com.native-instruments.Kontakt 4: Latency (Input: 1, Samplerate: 16000) device: 16, stream: 0, securityoffset: 21, buffer: 512, total: 549
26/04/12 11:44:30,514 [0x0-0x314314].com.yamaha.dspMixFx_UR824: Qt: QCursor: Cannot create bitmap cursor; invalid bitmap(s)
26/04/12 11:46:18,876 dspMixFx_UR824: -_continuousScroll is deprecated for NSScrollWheel. Please use -hasPreciseScrollingDeltas.
26/04/12 11:46:18,877 dspMixFx_UR824: -deviceDeltaX is deprecated for NSScrollWheel. Please use -scrollingDeltaX.
26/04/12 11:46:18,877 dspMixFx_UR824: -deviceDeltaY is deprecated for NSScrollWheel. Please use -scrollingDeltaY.
26/04/12 11:46:25,495 Audio MIDI Setup: Error loading /Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio: dlopen(/Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio, 262): no suitable image found. Did find:
/Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin/Contents/MacOS/DVCPROHDAudio: no matching architecture in universal wrapper
26/04/12 11:46:25,496 Audio MIDI Setup: Cannot find function pointer NewPlugIn for factory C5A4CE5B-0BB8-11D8-9D75-0003939615B6 in CFBundle/CFPlugIn 0x7f8a58c64620 </Library/Audio/Plug-Ins/HAL/DVCPROHDAudio.plugin> (bundle, not loaded)
26/04/12 11:46:25,496 Audio MIDI Setup: Error loading /Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere: dlopen(/Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere, 262): no suitable image found. Did find:
/Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin/Contents/MacOS/WireTapAnywhere: no matching architecture in universal wrapper
26/04/12 11:46:25,497 Audio MIDI Setup: Cannot find function pointer New_SHP_PlugIn for factory 834FC054-C1CC-11D6-BD01-00039315CD46 in CFBundle/CFPlugIn 0x7f8a58c62bd0 </Library/Audio/Plug-Ins/HAL/WireTapAnywhere.plugin> (bundle, not loaded)
26/04/12 11:49:19,828 com.apple.usbmuxd: _handle_timer heartbeat detected detach for device 0x2b-192.168.1.193:0!
26/04/12 11:49:28,068 com.apple.usbmuxd: _SendDetachNotification (thread 0x7fff76cf4960): sending detach for device 28:6a:ba:37:ed:9d@fe80::2a6a:baff:fe37:ed9d._apple-mobdev._tcp.local.: _BrowseReplyReceivedCallback got bonjour removal.