I only skimmed the db code but noticed some nsv_exists and nsv_set calls. Perhaps this is related to this AOLserver 4.0 bug that Andrew Piskorski submitted? (Still unassigned.)
"[ 712241 ] Creating empty nsv fails in AOLserver 4"
http://sourceforge.net/tracker/index.php?func=detail&aid=712241&group_id=3152&atid=103152