SEO

I am struggling with a query which is stretching my sql (geddit?)
knowledge to breaking point. I am storing data about railway accidents
and accident reports. I have the following tables:

tbllocations - stores locations of accidents
tblcompanies - stores the train operating companies for the accident
tblcauses - stores causes of accidents
tblresults - stores results of accidents
tblevents - stores the accidents themselves
tbldocuments - stores accident reports

Relationships are as follows:

tbllocations 1-to-many tblevents
tblcompanies many-to-many tblevents
tblcauses many-to-many tblevents
tblresults many-to-many tblevents
tblevents 1-to-many tbldocuments

therefore the many-to-many relationships have join tables, ie

tblcauseventjoin - fields causeID, eventID
tblresulteventjoin - fields resultID, eventID
tblcompanyeventjoin - fields companyID, eventID

I want to return only accidents which have a particular cause, a
particular company, a particular result, and where a related document
has been published (denoted by booPublished field in tbldocuments). I
have the following sql, which at first glance appears to work, but
which throws up the odd false negative:

SELECT tbllocations.txtLocation, ALIAS1.eventID, ALIAS1.datDate
FROM tbllocations
INNER JOIN ( tblevents AS ALIAS1 INNER JOIN tblcompanyeventjoin ON
ALIAS1.eventID = tblcompanyeventjoin.eventID ) ON
tbllocations.locationID = ALIAS1.locationID
INNER JOIN ( tblevents AS ALIAS2 INNER JOIN tblcauseeventjoin ON
ALIAS2.eventID = tblcauseeventjoin.eventID ) ON tbllocations.locationID
= ALIAS2.locationID
INNER JOIN ( tblevents AS ALIAS3 INNER JOIN tblresulteventjoin ON
ALIAS3.eventID = tblresulteventjoin.eventID ) ON
tbllocations.locationID = ALIAS3.locationID
WHERE tbllocations.locationID = '391'
AND tblcompanyeventjoin.companyID = '22'
AND tblcauseeventjoin.causeID = '1'
AND tblresulteventjoin.resultID = '3'
AND tbldocuments.booPublished = 'yes'
GROUP BY ALIAS1.eventID

Can anyone tell me a) where I am going wrong and, more importantly, b)
why?

GazK