Server log issue

I was looking through my server logs for the first time, trying to
trouble shoot something else, when I noticed this. About 90% of my
server log is filled with the same error line:

[07/02/06@09:55:32.066-0600] P-004032 T-005252 1 AS -- (Procedure:
'calcLaborHours bo/Labor.p' Line:11869) ** No ResourceGroup record is
available. (91)

Any ideas on what would cause this?