What steps will reproduce the problem?
1. open the Mailbox

What version of the product are you using?
r238

Do you have an error log of what happened?
Date: 2015-09-20 14:01:58
ID: 1
Error occured in: Global
Count: 1
Message: ..\AddOns\BankItems\BankItems.lua line 3835:
   attempt to index field 'Bag103' (a nil value)
Debug:
   BankItems\BankItems.lua:3835 BankItems_SaveMailbox()
   BankItems\BankItems.lua:1207
      BankItems\BankItems.lua:1151
Locals:
_ = nil
sender = nil
money = nil
daysLeft = nil
itemCount = nil
name = nil
count = nil
itemPointer = nil
numItems = 0
totalItems = 0
j = 0
moneyTotal = 0
subCount = 0
theTime = 1442750518
(*temporary) = nil
(*temporary) = "6.2.2.0"
(*temporary) = 4
(*temporary) = 18
(*temporary) = 4
(*temporary) = 4
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = 0
(*temporary) = 0
(*temporary) = 1
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = nil
(*temporary) = "attempt to index field 'Bag103' (a nil value)"
selfPlayer = <table> {
 Bag102 = <table> {
 }
 Bag105 = <table> {
 }
 Bag101 = <table> {
 }
 Bag4 = <table> {
 }
 Bag2 = <table> {
 }
 22 = <table> {
 }
 Bag8 = <table> {
 }
 Bag5 = <table> {
 }
 money = 103243114
 Bag1 = <table> {
 }
 Bag3 = <table> {
 }
 Bag100 = <table> {
 }
 Ver = "6.2.2.0"
 Bag7 = <table> {
 }
 Bag0 = <table> {
 }
 faction = "Horde"
 location = "Frostwall"
 NumBankSlots = 7
 TOC = 60200
 Bag6 = <table> {
 }
}
newTable = <function> defined @Interface\AddOns\BankItems\BankItems.lua:2850
ICON_Mailbox = "Interface\Icons\INV_Letter_02.png"
AdjustExpiredMail = <function> defined @Interface\AddOns\BankItems\BankItems.lua:5514
GetInboxHeaderInfo = <function> defined =[C]:-1
GetInboxItem = <function> defined =[C]:-1
GetInboxItemLink = <function> defined =[C]:-1
selfPlayerRealm = "Zuluhed"
delTable = <function> defined @Interface\AddOns\BankItems\BankItems.lua:2857
tremove = <function> defined =[C]:-1
bankPlayer = nil
BagContainerAr = <table> {
}
BagButtonAr = <table> {
}
TOC = 60200
BANKITEMS_VERSION = "6.2.2.0"

AddOns:
  InspectFix, v4.5.1
  Swatter, v5.21c.5521 (SanctimoniousSwamprat)
  Ace3, v
  Ailo, v
  Auditor2, v5.0.4
  BankItems, v6.2.2.0
  BrokerAuditor, v5.0.4
  CalendarKeyboardFixer, v1.2.2
  ConfirmLootRoll, v
  Coordinates, v1.19
  DailyGrind, v3.0
  DebugLib, v5.1.DEV.337(/embedded)
  idTip, v6.2.1
  ImprovedLootFrame, v3.6
  MasterPlan, v0.68
  MasterPlanA, vA
  Outfitter, v5.10b10
  Postal, v3.5.4
  Prat30, v3.5.16    
  Prat30HighCPUUsageModules, v
  Prat30Libraries, v
  RecountMitigation, v
  SlideBar, v5.21c.5521 (SanctimoniousSwamprat)
  Stubby, v5.21c.5521 (SanctimoniousSwamprat)
  WoWDBProfiler, v
  BlizRuntimeLib_enUS v6.2.2.60200 <none>
  (ck=28f)