WowAce

What steps will reproduce the problem?
1. type /mount
2. Go to the mount list
3. Click one of the mounts

What is the expected output? What do you see instead?
I'd expect to mark it as available to selection, but I get this message:

Date: 2009-08-25 08:29:24
ID: 1
Error occured in: Global
Count: 1
Message: ..\AddOns\Mountiful\Mountiful.lua line 904:
   Usage: GetNumCompanions(type)
Debug:
   [C]: ?
   [C]: GetNumCompanions()
   Mountiful\Mountiful.lua:904: Mountiful_nametonum()
   Mountiful\Mountiful.lua:564: CheckBox_OnClick()
   [string "*:OnClick"]:1:
      [string "*:OnClick"]:1
AddOns:
  Swatter, v5.6.4399 (KangaII)
  WowheadLooter, v30201
  Aloft, v2.8.5
  AucAdvanced, v5.6.4399 (KangaII)
  AucDb, v5.1.DEV.3583
  AucFilterBasic, v5.6.4399 (KangaII)
  AucFilterOutlier, v5.6.4399.2531
  AucMatchUndercut, v5.6.4399.2531
  AucScanData, v5.6.4399 (KangaII)
  AucStatClassic, v5.6.4399 (KangaII)
  AucStatHistogram, v5.6.4399 (KangaII)
  AucStatiLevel, v5.6.4399 (KangaII)
  AucStatPurchased, v5.6.4399 (KangaII)
  AucStatSales, v5.6.4399.2842
  AucStatSimple, v5.6.4399 (KangaII)
  AucStatStdDev, v5.6.4399 (KangaII)
  AucStatWOWEcon, v5.6.4399.2530
  AucUtilAHWindowControl, v5.6.4399.3311
  AucUtilAppraiser, v5.6.4399.2530
  AucUtilAskPrice, v5.6.4399.3175
  AucUtilAutoMagic, v5.6.4399.3142
  AucUtilCompactUI, v5.6.4399.2530
  AucUtilEasyBuyout, v5.6.4399.3583
  AucUtilItemSuggest, v5.6.4399.3108
  AucUtilPriceLevel, v5.6.4399.2545
  AucUtilScanButton, v5.6.4399.2530
  AucUtilScanFinish, v5.6.4399.2530
  AucUtilScanProgress, v5.6.4399.2530
  AucUtilSearchUI, v5.6.4399.3655
  AucUtilSimpleAuction, v5.6.4399.0
  AucUtilVendMarkup, v5.6.4399.2530
  Babylonian, v5.1.DEV.130
  BeanCounter, v5.6.4399 (KangaII)
  BonusScanner, v5.2
  BrokerBonusScanner, v1.2
  Carbonite, v3.22
  CarboniteTransfer, v1.01
  Clique, v126
  Configator, v5.1.DEV.130
  DBMCore, v
  DebugLib, v5.1.DEV.130
  Enchantrix, v5.6.4399 (KangaII)
  EnchantrixBarker, v5.6.4399 (KangaII)
  Gatherer, v3.1.14
  Grid, v1.30200.2009080501
  IceHUD, v1.5.12 (Revision: 434)
  Informant, v5.6.4399 (KangaII)
  Mountiful, v1.6.5 Beta
  NotesUNeed, v6.58.30200
  OmniCC, v2.5.6
  Outfitter, v4.8b6
  Overachiever, v0.46
  OverachieverTabs, v0.46
  PallyPower, vv3.2.4-release
  Skada, v1.2-20
  SkadaAbsorbs, v1.0
  SkadaCC, v1.0
  SkadaDamage, v1.0
  SkadaDamageTaken, v1.0
  SkadaDeaths, v1.0
  SkadaDebuffs, v1.0
  SkadaDispels, v1.0
  SkadaEnemies, v1.0
  SkadaFailbot, v1.0
  SkadaHealing, v1.0
  SkadaPower, v1.0
  SkadaThreat, v1.0
  Stubby, v5.6.4399 (KangaII)
  Titan, v4.2.9.30200 - Revision 309
  TitanAmmo, v4.2.9.30200
  TitanBag, v4.2.9.30200
  TitanClock, v4.2.9.30200
  TitanCoords, v4.2.9.30200
  TitanGoldTracker, v4.2.9.30200
  TitanLootType, v4.2.9.30200
  TitanPerformance, v4.2.9.30200
  TitanRegen, v4.2.9.30200
  TitanRepair, v4.2.9.30200
  TitanVolume, v4.2.9.30200
  TitanXP, v4.2.9.30200
  WinterTime, v1.81
  BlizRuntimeLib_enUS v3.2.0.30200 <us>
  (ck=939)

What version of the product are you using?
1.6.5beta

Do you have an error log of what happened?
See above.

Please provide any additional information below.

Forgot to mention this:

On my main, I got the message the first time, but things worked fine after that.

With one of my alts, as soon as I got the Charger (paladin, level 20), I tried to use it and got the message again. Closing the window and opening it again showed no mounts at all.