This is a 2 parter for you.
1. To determine who has what locked:
In Query Analyzer type or paste this in:
use msllockdb
go
select sessionid, tablename, rowid from maclocks
exec sp_who
2. To clear the Buyer/Planner lock if it is caused by an abnormal exit:
In Macola: System Manager>Processes>Initialize Distribution>PO Files>POBUYERP (PO buyer print file)
Hope this helps