'unspecified error' ctd on battlemap load for most sieges

[sapi]

Details and all that:
English M2TW 1.2 (not a fresh install but no modding done on the original copy except unlocking factions)
Windows Vista (32 bit)
CTD occurs loading certain siege assault/sally maps, but not on others. So far every siege I've tried to play as the ERE except for Trezibond has caused the error.
The game crashes with the usual 'unspecified error' message. Vanillia M2TW was not doing this, last I checked.
Log file for the latest crash (pretty useless )

Spoiler Alert, click show to read: 

22:31:58.513 [system.rpt] [always] CPU: SSE2
22:31:58.514 [system.rpt] [always] ==== system log start, build date: Apr 23 2007 version bld-medieval2-update2-84 (37970) ===
22:31:58.520 [system.io] [always] mounted pack packs/data_0.pack
22:31:58.521 [system.io] [always] mounted pack packs/data_1.pack
22:31:58.523 [system.io] [always] mounted pack packs/data_2.pack
22:31:58.525 [system.io] [always] mounted pack packs/data_3.pack
22:31:58.526 [system.io] [always] mounted pack packs/data_4.pack
22:31:58.526 [system.io] [always] mounted pack packs/localized.pack
22:45:02.535 [system.rpt] [error] Medieval 2: Total War encountered an unspecified error and will now exit.

It's honestly hard to label the bug as reproducible; the only initiator of sieges there is in this campaign at the moment is the AI, and it's hardly predictable enough to give me the same situation to test each time I reload. Likewise, while I do know that it seems to happen in some settlements and not in others, I've no idea what the unifying factor is in the ones that crash

EDIT: A quick browse suggests I'm not the only one, however

EDIT2: It just struck me that I don't actually have kingdoms installed at the moment. Would BC be trying to reference some of that data?

EDIT3: Fixed by a full reinstall > 1.21 > 1.3 > BC