[Zope] too many open files

Help! Zope 2.1.6 refuses to work in the middle of an external method on my i386 running under OpenBSD 2.7. Is says: ---------------------------------------------------- OSError [Errno 24] Too many open files: '/var/tmp/@6067.265' ---------------------------------------------------- I've never ever seen this problem before and this external method used to work well until some minutes ago. Now the error keeps reappearing even after rebooting and also other external methods that used to run well now deliver the same message. Does anybody have suggestions how to diagnose/cure this problem? --Ragnar