The problem is the OBSPROJ table gets out of synch between the PROJ and WBS values. If you are using Oracle, you can run the following query to find places where the PROJ and WBS don't line up:

* Find Bad OBSPROJ that can be fixed */

select o.obs_id, o.proj_id, o.wbs_id, p.proj_short_name, w.wbs_short_name, wnew.wbs_id new_wbs_id
from obsproj o, project p, projwbs w , projwbs wnew
where o.proj_id=p.proj_id and w.wbs_id=o.wbs_id
and p.proj_short_name<>w.wbs_short_name
and wnew.wbs_short_name(+)=p.proj_short_name and wnew.wbs_short_name is not null

Assuming that your WBS (EBS) is named the same as your PROJECTS, you can run the following script:

update obsproj op set op.wbs_id=(select wbs_id from projwbs where wbs_short_name=(select proj_short_name from project where proj_id=op.proj_id))
where (op.obs_id, op.proj_id) in (select o.obs_id, o.proj_id
from obsproj o, project p, projwbs w , projwbs wnew
where o.proj_id=p.proj_id and w.wbs_id=o.wbs_id
and p.proj_short_name<>w.wbs_short_name
and wnew.wbs_short_name(+)=p.proj_short_name and wnew.wbs_id is not null)

If your DBA wants to debug the problem, they can just look at some of the select queries in the POPULATE_UACCESS trigger and see where the duplicates are occurring if the above doesn't fix the problem.