ADB is working, but fastboot is not on Mac OS X with HTC Desire Z

The adb devices command is working for me, the fastboot devices command is not (Mac OS X Mavericks, SDK downloaded yesterday, the phone is an HTC Desire Z): $ sudo fastboot -i 0x0bb4 -p 0x0c91 devices $ fastboot -i 0x0bb4 -p 0x0c91 devices $ fastboot devices $ adb devices List of devices attached HT0C5RT00804 device $ adb shell # So fastboot doesn't list devices, whatever I try (sudo, or specifying -i and -p options), while ADB works just fine. I found vendor and product IDs via Mac OS X system information. ADB working seems to indicate that communication between my laptop and the phone does work fine. How can I get fastboot to work? **Background info:** I'm trying to install CyanogenMod on a HTC Desire Z. Part of the procedure I'm following is described here: http://wiki.cyanogenmod.org/w/HTC_Desire_Z:_Firmware_Downgrade_(Gingerbread) I get stuck at the fastboot oem rebootRUU step: $ fastboot oem rebootRUU (hangs, I gave up after 20 minutes), and I think that is due to fastboot not working. Any other ideas on how to get past this appreciated?