One of your items is missing a record in timCostTier (likely).  Without good SQL knowledge this will be hard to fix.  If you can figure out which item it is you might be able to do a cost tier adjustment to create a timCostTier record (might depend on your costing method).  I would probably contact your reseller or Sage support.  If you feel good about SQL then the first step would be to run a trace on the trigger object and back track it from there.  Good luck.

Thanks for the reply.  We did end up figuring out tracing back through the trigger.