files missing from smart playlists

[tmacca]

I have created alphabetized smart playlists as follows:

Series - A
Series - B
........
Series - Z

Movies - A
Movies - B
......
Movies - Z


The criteria for each is basically the same:
Match ALL of the following
title STARTS WITH A
File Path CONTAINS series

However, random files are missing from each playlist. In some cases, half a particular series will be missing, but the other half is there. For example:

Alcatraz.S01E01.avi
Alcatraz.S01E02.avi
....
Alcatraz.S01E07.avi

are in the playlist, but episodes 8 onwards are not. I have tried maintaining the playlist, renaming the file, with no joy

Any ideas? Is there anything in the logs I could check?


EDIT. Actually, the smart playlists don't seem to be the problem. The problem files are missing from the library, period. If I look in the 'All Video Files' playlist, they aren't there either