Sun provide (although not officially supported) a tool called iscda for analysing dumps produced when a system crashes. The script uses adb to produces a readable report from the dumps produced. By reading through this report, it should become clear what caused the crash. To use the script do the following:

 1. Copy the csript to the directory containing the vmcore and unix files
    e.g. /var/crash
 2. run the script as follows: ./iscda unix.# vmcore.# > /tmp/iscda.output
 3. Check through the iscda.output report
 4. You can also run it against a live system as follows:
    ./iscda /dev/ksyms /dev/mem > /tmp/iscda.output