To VogonPoet: Well if whatever it says in the report's Record Source property is right, then yes, I'm absolutely sure
To JoeMiller: I was trying to reduce the filesize and make sure there was no sensitive data in the database, when I thought I'd stumbled upon the solution. I removed the surplus reports and queries and as I was reducing some of the field sizes in the main ("Gaps"

table, I realised the file wasn't getting any smaller. I then remembered that it needs to be compacted, and after doing this, presto!, the particular job I'd been looking at which shouldn't have been in the report had gone! Then on closer inspection, I saw that there were several others which had appeared which were also 'Closed'!
Anyway, I got the total database size down to 2MB, so if this isn't too big for you to download, you can pick it up from the Public Folder of my Yahoo Briefcase at
(if it's still too big, let me know and I'll see if I can make it any smaller).
Before you make any changes follow these instructions to see the problem: (by the way, I'm using Access 97, so I don't know if it'll be the same if you're using 2000)
The report in question is "Open Gaps (by Category) (brief) 170801". Open this first, and note the Gap numbers 1392 and 1382 on the first page (there are others on other pages too). Now if you look in the query on which the report is based, "Rpt: Open Gaps (by Category) (Pt 2)" (order the Gap_ref column to be safe), you will see that these numbers do not appear. Also, if you open the form, "Gaps form", and find the records with these numbers in the Gap ref field (alternatively, use the underlying tables, "Gaps" and "Gap Status records"

, you can see that the latest status of these gaps is "CLOSED" (code 7).
Any (even minor) changes made to the tables can alter the report's output, and at one point I thought it had output all the correct ones, then noticed that an open job (Gap 112) had disappeared from the report! Because of this, I really need to try to understand what is causing the problem, rather than finding a way to apparrently fix it, as I obviously don't want this to recurr in the future, or to miss any wrong missing/added jobs.
P.S. I know the two queries which drive the report are set up in a slightly strange way, but: a.) this is partly because the (part1) query is also used for other reports. b.) I still see nothing which would pose a problem, or explain the presence of records in the report which aren't in the query results.
Thanks for your efforts.