Fatal Graphics Error?

[The Mouth]

I'm not sure why this is happening but my game keeps crashing during this particularly heated siege battle with a "Fatal Graphics Error" and it suggests to lower my settings despite the fact that my computer could easily run a 10,000 man battle in Shogun 2. The two times this error has occurred is when 1. The initial clash of my defending forces with their attacking forces and 2. At the end of the battle when I was running down enemy soldiers. The battle itself features around 5000 troops (1500 of which are mine). Any suggestions?

[The Mouth]

Nevermind, I eventually managed to make it through the battle without the game crashing. Haven't encountered the bug since.

[The Mouth]

Once again I've encountered this damn bug...

And once again its happened during a very large battle. I'm not sure if this will help but heres the system log:

17:13:19.728 [system.rpt] [always] CPU: SSE2
17:13:19.734 [system.rpt] [always] ==== system log start, build date: Aug 3 2007 version bld-medieval2-kingdoms-104 (45562) ===
17:13:19.737 [system.io] [always] mounted pack packs/data_0.pack
17:13:19.738 [system.io] [always] mounted pack packs/data_1.pack
17:13:19.738 [system.io] [always] mounted pack packs/data_2.pack
17:13:19.739 [system.io] [always] mounted pack packs/data_3.pack
17:13:19.739 [system.io] [always] mounted pack packs/data_4.pack
17:13:19.739 [system.io] [always] mounted pack packs/localized.pack
17:15:28.006 [game.script] [error] Script execution error for <label_unit>, at line 12594, in mods/SS6.3/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
label_unit referenced non-existent unit
17:15:28.007 [game.script] [error] Script execution error for <define_unit_group>, at line 12618, in mods/SS6.3/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
Error in battle script command 'define_unit_group': invalid unit label 'unit19'.
17:23:29.711 [game.script] [error] Script execution error for <if>, at line 20858, in mods/SS6.3/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
invalid unit label 'General3'
when testing <I_UnitStatus> condition
17:23:29.711 [game.script] [error] Script execution error for <if>, at line 20861, in mods/SS6.3/data/world/maps/campaign/imperial_campaign/campaign_script.txt:
invalid unit label 'General3'
when testing <I_UnitStatus> condition