WowAce

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>

Invite in combat is a blizz bug. andreasg cannot do something about it.