Occasionally getting an error when I loot monsters or other items (see below). This started after the last patch. Any ideas?

Date: 2008-05-16 09:08:45
ID: 51
Error occured in: Global
Count: 1
Message: ..\AddOns\Gatherer\Swag\LibSwag.lua line 212:
attempt to concatenate global 'COPPER' (a nil value)
Debug:
[C]: ?
Gatherer\Swag\LibSwag.lua:212:
Gatherer\Swag\LibSwag.lua:203
(tail call): ?
Gatherer\Swag\LibSwag.lua:71: OnEvent()
Gatherer\Swag\LibSwag.lua:392:
Gatherer\Swag\LibSwag.lua:392
AddOns:
AdvancedTradeSkillWindow
agUnitFrames, v05-01-07
AutoDecline, v1.5.20300
Bagnon, v1.5.2
BagnonForever, v1.0.0
BagnonTooltips
BeanCounter, v5.0.PRE.3104 (BillyGoat)
BigWigs, v2.0 r72870
Bongos2, v1.10.1
Bongos2ActionBar
Bongos2CastBar
Bongos2MapBar
Bongos2RollBar
Bongos2Stats
Bongos2XP
Cartographer, vr73088
ChatMOD, v118
CTViewport, v2.4 (CTMod 2.0)
EnhTooltip, v5.0.PRE.3104
FuBarAmmoFu, v2.0
FuBarClockFu, v3.0
FuBarDurabilityFu, v2.0
FuBarExperienceFu, v1.1 $Revision: 65606 $
FuBarGarbageFu, v2.0.$Revision: 70904 $
FuBarLocationFu, v3.0
FuBarMoneyFu, v20400-1
FuBarRestFu, v2.0
FuBarToFu, v2.0
FuBar, v60201
Gatherer, v3.1.1
Grid, v71400
GroupCalendar, v3.4.4
Informant, v5.0.PRE.3104
LightHeaded, v233
LightHeadedDataD, v233
MBB
Omen, vOmen r73994 / Threat-2.0 r73937
oRA2, v2.0.$Revision: 70972 $
Outfitter, v4.2.1
Postal, v2.1 r73730
Quartz, v0.1.0
RecipeRadar, v1.27
RecipeBook, v2.4.0d
Recount, v73484
SatrinaBuffFrame, v2.8
sct, v6.1
sctd, v3.1
simpleMinimap, v20100-6
Stubby, v52
Swatter, v5.0.PRE.3104
TankPoints, v2.7.0 (r73669)