Kernel Panic

After several panic-free weeks, I got a kernel panic this morning. I finally got a panic log written:

panic(cpu 0): IOSCSIPeripheralDeviceType05: attached at free()
Latest stack backtrace for cpu 0:
      Backtrace:
         0x000856CC 0x00085AFC 0x000287A8 0x00214E00 0x19C92464 0x19C8B218 0x1A345954 0x1A349BF8
         0x1A34AFB0 0x0003EAB4 0x0003E9BC
      Kernel loadable modules in backtrace (with dependencies):
         com.apple.iokit.IOSCSIMultimediaCommandsDevice(1.2.2)@0x1a340000
            dependency: com.apple.iokit.IODVDStorageFamily(1.2)@0x1a28e000
            dependency: com.apple.iokit.IOSCSIBlockCommandsDevice(1.2.2)@0x1a117000
            dependency: com.apple.iokit.IOCDStorageFamily(1.2)@0x1a231000
            dependency: com.apple.iokit.IOSCSIArchitectureModelFamily(1.2.2)@0x19c87000
            dependency: com.apple.iokit.IOStorageFamily(1.2.3)@0x19d47000
         com.apple.iokit.IOSCSIArchitectureModelFamily(1.2.2)@0x19c87000
Proceeding back via exception chain:
   Exception state (sv=0x01813C80)
      PC=0x00000000; MSR=0x0000D030; DAR=0x00000000; DSISR=0x00000000; LR=0x00000000; R1=0x00000000;
 XCP=0x00000000 (Unknown)

Kernel version:
Darwin Kernel Version 6.3:
Sat Dec 14 03:11:25 PST 2002; root:xnu/xnu-344.23.obj~4/RELEASE_PPC

Note that I have no SCSI devices. Has anyone seen this?