annoying error in form

I have a form that is based on a query. No "sub" queries within this query.
However, for some reason, I am now getting a frequent error that seems to be
more of a nuisance than anything. Almost every time a go from record to
record within the form, or update an entry I get the following:
"The value you entered isn't valid for this field." It doesn't seem to
matter which field I update, search on, or have the cursor at the time I go
from record to record.

Any ideas as to why this is happening would be most appreciated.

I am pasting the SQL for the query I am using.
SELECT tblBaseline.[LIMTS#], tblBaseline.AssessmentType,
tblBaseline.[Assessment Title], tblBaseline.ScopeDescription,
tblBaseline.OwningAD, tblBaseline.Org, tblBaseline.EstimatedStartDate,
tblBaseline.Quarter, tblBaseline.LANLTeamLead, tblLASOpart.LASOLead,
tblLASOpart.AM, [zlookup AssessmentStatus].Status, tblBaseline.[Date
Completed Field], tblLASOpart.[Form A Complete], tblLASOpart.[Form B
Complete], tblLASOpart.datFormA, tblLASOpart.datFormB,
tblAttachA.DateEntered, tblAttachB.Entered
FROM (((tblBaseline LEFT JOIN tblLASOpart ON tblBaseline.[LIMTS#] =
tblLASOpart.[LIMTS#]) LEFT JOIN [zlookup AssessmentStatus] ON
tblBaseline.Status = [zlookup AssessmentStatus].ID) LEFT JOIN tblAttachA ON
tblLASOpart.[LIMTS#] = tblAttachA.LIMTSnum) LEFT JOIN tblAttachB ON
tblLASOpart.[LIMTS#] = tblAttachB.LIMTSnum
ORDER BY tblBaseline.[LIMTS#];