OK, so I've made an opening door which works absolutely fine ingame except for the fact that you can shoot right through it, even though I've added the collision primatives as instructed in the tutorial: Anyone know if there's something I could have missed. I definitely haven't forgotten to export them with the rest of the model, and I don't think you were supposed to freeze them or anything, so has anyone got any ideas?

first: if you freeze primitives, they will no longer work.
did you activate the pointviewoptions in the viewports or did you envelope them? if you did, then thats the reason.
generally you can check if a primitive works by opening its propertypage. if you still have the primitive options (subdivisions, lenght etc.) and changing them has the right effect they should be intact.
in your case i would make two new primitives and do nothing with them except scaling, rotating and translating, put them under the bones and export. it should work then.
you can also see that the primitives are recognized if you get the red "argument 0 invalid"-error at the bottom of the screen after exporting.

Well I think they're certainly recognized because I do get that error before I export, hmm.
I made the collision primatives by duplicating the original polygons, renaming them and sticking them under the corresponding 'bone' section. Would this have any adverse effect, or is it necessary to make new primitives from scratch?

you mean extracting polygons?
if you make "primitives" by extracting polygons they just cant work because they never were primitives
primitives can only be created through xsis create>primitives menusection.

Not sure, but I mean duplicating a previous primitive polygon, that I made. That's not extracting, is it?

so you duplicate the model and not the polygons?

To be sure and because they are not too complex you should make two new primitives.
Also you may want to merge all the non-moving parts and call it just collision or the frame won't have any collision either.

I duplicated only the two square polygons, door_left and door_right to make the collision parts because they were very akward sizes and I wasn't sure how to scale the new polygons to the same size.
Just me being lazy really, but I'll give creating new ones a go and try to merge all the non moving parts too. Thanks for the tips Probably won't be able to have a go at this for another day or so because I've got a chemistry exam tomorrow and I've more been concentrating on that. I'll post back if it works or not tomorrow, but thanks anyway

EDIT
That worked perfectly, thanks for both of you's help!