teame06's code and mine were equivalent. In fact, I had a sneaking suspicion that there was something deeper going on. So I installed AMX Mod X on my Windows machine and compiled my original script on it. It worked fine (as does team06's). The fault lay not in the script but in cstrike.h. The error caused cs_get_armoury_type to work on Windows, but not on Linux.
For anyone wanting to use cs_get_armoury_type or cs_set_armoury_type right now on Linux you will need to change line 106 in cstrike.h from
Code:
#define OFFSET_ARMOURY_TYPE 34 + EXTRAOFFSET
to
Code:
#define OFFSET_ARMOURY_TYPE 34 + EXTRAOFFSET_WEAPONS
and then recompile.