WowAce

What version of the product are you using?
ag_UnitFrames v20090104

Do you have an error log of what happened?

["message"] = "...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: aUFFontString116:SetText(): Font not set",
["count"] = 1,
["addons"] = "  Swatter, v5.2.4013 (DingoII)\n  agExtras, v09-19-07\n  agUnitFrames, v2009-01-04\n  AtlasLoot, vv5.03.02\n  AuldLangSyne, v2.0\n  AuldLangSyneFriendList, v2.0\n  Bartender4, v4.2.5\n  Broker2FuBar, v1.0\n  Cartographer, v2.0\n  CartographerCoordinates, v2.0\n  CartographerLookNFeel, v2.0\n  CartographerWaypoints, v2.0\n  CartographerZoneInfo, v2.0\n  DBMCore, v\n  Decursive, v2.4_beta_3\n  ErrorMonster, v3\n  FluidFrames, v2.2\n  FuBar, v\n  FuBarDurabilityFu, v2.11\n  GatherMate, v1.0.13\n  Outfitter, v4.4b4\n  PerfectRaid, v185\n  PlayerLinkMenu, v\n  Portfolio, v0.6\n  RangeRecolor, v2.1\n  RatingBuster, v\n  RecipeBook, v\n  SpamSentry, v20090212\n  TipTac, v08.12.05\n  (ck=28e)\n",
["timestamp"] = "2009-02-14 14:21:19",
["context"] = "Global",
["stack"] = "[C]: ?\n[C]: in function `SetText'\n...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: in function `func'\nInterface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:187: in function <Interface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:182>\n",

["message"] = "...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: aUFFontString119:SetText(): Font not set",
["count"] = 1,
["addons"] = "  Swatter, v5.2.4013 (DingoII)\n  agExtras, v09-19-07\n  agUnitFrames, v2009-01-04\n  AtlasLoot, vv5.03.02\n  AuldLangSyne, v2.0\n  AuldLangSyneFriendList, v2.0\n  Bartender4, v4.2.5\n  Broker2FuBar, v1.0\n  Cartographer, v2.0\n  CartographerCoordinates, v2.0\n  CartographerLookNFeel, v2.0\n  CartographerWaypoints, v2.0\n  CartographerZoneInfo, v2.0\n  DBMCore, v\n  Decursive, v2.4_beta_3\n  ErrorMonster, v3\n  FluidFrames, v2.2\n  FuBar, v\n  FuBarDurabilityFu, v2.11\n  GatherMate, v1.0.13\n  Outfitter, v4.4b4\n  PerfectRaid, v185\n  PlayerLinkMenu, v\n  Portfolio, v0.6\n  RangeRecolor, v2.1\n  RatingBuster, v\n  RecipeBook, v\n  SpamSentry, v20090212\n  TipTac, v08.12.05\n  (ck=28e)\n",
["timestamp"] = "2009-02-14 14:21:55",
["context"] = "Global",
["stack"] = "[C]: ?\n[C]: in function `SetText'\n...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: in function `func'\nInterface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:187: in function <Interface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:182>\n",

["message"] = "...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: aUFFontString122:SetText(): Font not set",
["count"] = 1,
["addons"] = "  Swatter, v5.2.4013 (DingoII)\n  agExtras, v09-19-07\n  agUnitFrames, v2009-01-04\n  AtlasLoot, vv5.03.02\n  AuldLangSyne, v2.0\n  AuldLangSyneFriendList, v2.0\n  Bartender4, v4.2.5\n  Broker2FuBar, v1.0\n  Cartographer, v2.0\n  CartographerCoordinates, v2.0\n  CartographerLookNFeel, v2.0\n  CartographerWaypoints, v2.0\n  CartographerZoneInfo, v2.0\n  DBMCore, v\n  Decursive, v2.4_beta_3\n  ErrorMonster, v3\n  FluidFrames, v2.2\n  FuBar, v\n  FuBarDurabilityFu, v2.11\n  GatherMate, v1.0.13\n  Outfitter, v4.4b4\n  PerfectRaid, v185\n  PlayerLinkMenu, v\n  Portfolio, v0.6\n  RangeRecolor, v2.1\n  RatingBuster, v\n  RecipeBook, v\n  SpamSentry, v20090212\n  TipTac, v08.12.05\n  (ck=28e)\n",
["timestamp"] = "2009-02-14 14:23:26",
["context"] = "Global",
["stack"] = "[C]: ?\n[C]: in function `SetText'\n...terface\\AddOns\\ag_Extras\\modules\\castbar\\castbar.lua:206: in function `func'\nInterface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:187: in function <Interface\\AddOns\\ag_UnitFrames\\ag_UnitClass.lua:182>\n",

A very similar if not identical problem is still present in the latest version. Encountered it only just yesterday. After joining a party (having the party cast bar visible) this error suddenly started spamming. I got disconnected while in a party the same day, but don't remember if it was before or after, but that might be connected with the problem. If not exactly this, a very similar problem is present. Will post my trace is it happens again and I'm not too annoyed to just disable it.

I am getting many of the same errors when castbars on the raid ui are turned on. It happened 378 times in one wintergrasp lol. The errors are all pretty similar, but one particular seemed to be most common under heavy pvp activity.

They almost all were in castbar.lua and Font Not Set and many different lines, 206, 180, 298, 318, 164, 284, 174, 206, 247. There are more, but not sure of time when they occurred. I'm using r700 currently and getting these.

Also in castbar.lua is line 275 saying "attempt to index field 'CastBar' (a nil value)"