I guess you installed dotlrn from oacs-5-1 over an acs-core checked out from oacs-5-2.
http://cvs.openacs.org/cvs/openacs-4/packages/acs-tcl/tcl/site-node-apm-integration-procs.tcl?r1=1.10.2.1&r2=1.10.2.2&only_with_tag=oacs-5-2
Cheers, Victor Guerra.