problem with tile index files and shape files

[Emilio Mayorga]

I used ogrtindex to create a tile index file for a set of 7 polygon 
shape files. These files (land cover types in country tiles) were 
supposed to be identical in structure, but one of them is slightly 
different, and that's the only one that Mapserver doesn't display when I 
use a layer that refers to the tile index. If I refer to that deviant 
shape file directly in a separate layer, with everything else the same 
(I use FILTER expressions), it displays fine.

I'm using Mapserver 4.0 and OGR from October 2003 (I really need to 
update one of these days...). Using ogrinfo on one of the good shape 
files, I get this summary info:
AREA_KM2: Real (12.6)
IDUNESCO: String (25.0)
DESCRIPCIO: String (75.0)
PAIS: String (15.0)

But on the bad shape tile I get:
IDUNESCO: String (16.0)
DESCRIPCIO: String (150.0)
AREA_KM2: Real (13.6)
PAIS: String (15.0)

Fields are in a different order, and are defined just slightly 
differently (I'm using FILTERITEM "IDUNESCO" in my layer). Also, the bad 
shape file is grouping lots of polygons into few multipolygons, while 
the other shape files seem to have individual polygons. (ogrinfo gives 
"Geometry: Polygon" for both, though).

Can anyone suggest a way to tweak the bad shape file so it plays nice 
with MapServer tile indices?

Thanks!

-Emilio Mayorga