What steps will reproduce the problem?
1. Be solo or with a partial party
2. Get in combat, or anyone in the party or the person you invite be in combat
3. Errors

What is the expected output? What do you see instead?
party joins without issue.  Lots of errors

What version of the product are you using?
r667

Do you have an error log of what happened?
[2008/11/21 00:01:15-45-x1]: ag_Extras-09-19-07\modules\castbar\castbar.lua:260 aUFFontString247:SetText(): Font not set
ag_Extras-09-19-07\modules\castbar\castbar.lua:260 in function `UpdateCastBar'
ag_Extras-09-19-07\modules\castbar\castbar.lua:87 in function `?'
ag_UnitFrames-2008-08-06\ag_UnitClass.lua:121 in function `ExecModuleMethods'
ag_UnitFrames-2008-08-06\ag_UnitClass.lua:505 in function `UpdateAll'
ag_UnitFrames-2008-08-06\ag_UnitClass.lua:159 in function <Interface\AddOns\ag_UnitFrames\ag_UnitClass.lua:151
<in C code>: in function `Show'
Interface\FrameXML\SecureTemplates.lua:647 in function <Interface\FrameXML\SecureTemplates.lua:559
Interface\FrameXML\SecureTemplates.lua:854 in function `SecureGroupHeader_Update':
Interface\FrameXML\SecureTemplates.lua:443 in function `SecureGroupHeader_OnEvent':
<string>:"*:OnEvent":1: in function <[string "*:OnEvent"]:1>
<in C code>: ?

[2008/11/21 00:01:15-45-x37]: ag_Extras-09-19-07\modules\castbar\castbar.lua:164 aUFFontString248:SetText(): Font not set
ag_Extras-09-19-07\modules\castbar\castbar.lua:164 in function `func'
ag_UnitFrames-2008-08-06\ag_UnitClass.lua:187 in function <Interface\AddOns\ag_UnitFrames\ag_UnitClass.lua:182