one way would be to rebuild the kernel with
Code:
options COMPAT_FREEBSD6 # Compatible with FreeBSD6
never tried it but it *might* work.
the hard way would be to reinstall everything after you update your ports tree.
there might be other solutions out there but this are the only ones that come in mind right now.
and you should post more specific information (logs, err messages, etc) so more skilled people in here will be able to help you.
/v