Under current as of today (and previously under 1.6U) the pkgsrc
lsof seems to be broken:

===========================================================================
capo { /usr/pkgsrc/sysutils/lsof } # lsof
lsof: can't read process table: proc size mismatch (61696 total, 804 chunks)
capo { /usr/pkgsrc/sysutils/lsof } # which lsof
/usr/pkg/sbin/lsof
capo { /usr/pkgsrc/sysutils/lsof } # ls -l `which lsof`
-rwxr-sr-x  1 root  kmem  112300 Aug 15 15:53 /usr/pkg/sbin/lsof*
capo { /usr/pkgsrc/sysutils/lsof } # 
===========================================================================

   The kernel and userland matched in both cases.

					Gary D. Duzan