The bus error message is a bit concerning. It may indicate the system has trouble writing to the disk. You should review your messages and/or kernel log files in /var/log or /var/adm and check for other disk related errors.
You could try copying the contents of the aliases file into a new file, removing the old one, renaming the new file to aliases and then running newaliases again.
This would put a new file ona different section of disk and may allow you to rebuild your aliases.
Either way, check for errors, and possible to a fsck on the affected disk asap, after making a backup of any data possible.
Did it ever work, or is this a new install/upgrade? Did you compile it, or did you install a binary version?
What version of sendmail?
If it's not a disk write problem, it might be a problem with the binary.
BTW: Welcome to the board, Steve.
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