I have done an upgrade from v5.6 to 6.0b3 without seeing the same issue, but not a restore. Where you restoring from tape or desktop backup?
Did you use v6.03 and apply the available updates to it?
Don't forget to run:
/sbin/e-smith/signal-event post-upgrade
/sbin/e-smith/signal-event reboot
If you think it's a bug, don't forget to send it to smebugs@mitel.com
If it's still a problem, you may want to revert back to SME5.6 and wait for a response from your bug report.