The reference material states:

pls-00225, subprogram or cursor reference '%S' is out of scope.

Means that there is a problem resolving a object reference or variable name in the plsql program.
Check for duplicate variable declarations, or objects on the sys, system and the user schema, for any possible conflicts.
Select object_name, object_type, owner from dba_objects where object_name like '%'; should
help you identify the different objects existent in your system and the different schemas with the same name and that may be causing the reference conflict.

I also saw this out there on the web.
http://www.edhanced.com/ask-mred/?q=node/view/53. So it may be that Oracle thinks you want to use the built in LOG function. By putting the userid in front, Oracle resolves the name to a different object.

HTH,
Pete