[Zope] upgrade issue: ImportError: cannot import name MUCH_RING_CHECKING

just upgraded to zope-2.6.0_1 from the /usr/ports on my FreeBSD 4.7 Stabel machine. cant start now. why? typhoon# ./start ------ 2003-04-08T13:54:14 PANIC(300) z2 Startup exception Traceback (innermost last): Module __main__, line 580, in ? Module <string>, line 1, in ? Module Zope, line 21, in ? Module ZODB, line 43, in ? Module ZODB.DB, line 20, in ? Module ZODB.Connection, line 18, in ? ImportError: cannot import name MUCH_RING_CHECKING typhoon# pwd /usr/local/www/Zope typhoon# -- Net Enabled (http://www.enabled.com)