From gypsybug:

Ok. We did a few different things to try and get errors to occur and we named the files according to what we were testing. We are including them all, even if we didn't get a popup or chat error just in case it's helpful.

One thing we seemed to notice. There is a DEFINITE issue with having a Cenarion Circle toon in the Sisters of Elune server guild, or vice versa, a Sisters of Elune toon in the Cenarion Circle server guild. Most of our trouble came from this. We had PERFECT success when testing an SoE toon in the SoE guild talking to a CC toon in the CC guild. In this instance, both toons could see the guild chat of the other guild (and the toons were not officers).

When a CC server toon was in the SoE server guild and an SoE server officer spoke in guild chat, the CC server toon saw both the regular guild chat [G] and the ([Guild]) chat right underneath in duplicate.

Here is what we had going for each file.

1. Cenarion Circle toon in the CC guild talking to a Sisters of Elune toon in the SoE guild. - worked fine no errors noted. only one where it was perfect. These were non-officer toons.
2. Cenarion Circle toon in SoE guild talking to a Cenarion Circle officer in the CC guild - in this case the SOE guild toon saw the officer's message but the officer did not see the SOE guild toon's message.
3. Cenarion Circle toon in the Sisters of Elune guild talking to SoE officer in SoE guild - this one generated the odd duplicates for the Cenarion Circle toon mentioned above. In other words both were in the same guild, but the cenarion toon saw duplicated guild chat from the officer, with [G], and [Guild} prefacing the duplicates.
4. Cenarion Circle toon in Sisters of Elune guild talking to SoE toon in CC guild - we did this one specifically to test whether there was an issue with connected realm toons being in the opposite connected realm guild. This didn't work AT ALL. Neither could see the guild chat of the other.

Number 1 is where we tested the exact opposite. Having matching toons in matching guilds and it worked perfect.

1. SoE toon in the CC guild talking to an SoE officer in the SoE guild - the toon could see what the officer said but the officer could not see what the toon said. This is the reverse of number 2, and the results correspond.
2. SoE toon in CC guild talking to CC toon in SoE guild - didn't work at all - nothing nada and we got errors. This is the same as 4, but the log is from the opposite toon's side.

7.SoE toon in SoE guild talking to CC officer in cc guild - .again the toon could see the officer speaking but not the opposite.

We didn't test the O-chat in a situation similar to number 4 where both were officers. We'll look into this if you like.

Thanks! Let me know how our guilds can be of further assistance. We are happy to test your beta as you go.

CC toon, CC guild:

Date: 2014-09-17 22:16:42
ID: 1
Error occured in: Global
Count: 1
Message: ..\AddOns\GreenWall\GreenWall_Core.lua line 1486:
   bad argument #2 to 'format' (string expected, got nil)
Debug:
   [C]: format()
   GreenWall\GreenWall_Core.lua:1486: GreenWall_OnEvent()
   [string "*:OnEvent"]:1:
      [string "*:OnEvent"]:1
Locals:
(*temporary) = "Rx<GUILD(%s), %s>: %s"
(*temporary) = nil
(*temporary) = "Woad-CenarionCircle"
(*temporary) = "that was the greenwall developer who is working to connect our 2 guild chats"
(*temporary) = "string expected, got nil"

AddOns:
  Swatter, v5.20.5464 (RidiculousRockrat)
  DebugLib, v5.1.DEV.337(/embedded)
  GreenWall, v1.5.0-beta.1
  Stubby, v5.20.5464 (RidiculousRockrat)
  WIM, v3.6.18
  BlizRuntimeLib_enUS v5.4.8.50400 <us>
  (ck=c9)

CC toon, SoE guild:

Date: 2014-09-17 22:29:43
ID: 1
Error occured in: Global
Count: 1
Message: attempt to concatenate a nil value
Debug:
   [C]: strjoin()
   GreenWall\GreenWall_Core.lua:568:
      GreenWall\GreenWall_Core.lua:516
   GreenWall\GreenWall_Core.lua:1489: GreenWall_OnEvent()
   [string "*:OnEvent"]:1:
      [string "*:OnEvent"]:1
Locals:
(*temporary) = "#"
(*temporary) = "C"
(*temporary) = "#"
(*temporary) = nil
(*temporary) = "##testing"
(*temporary) = ""
(*temporary) = "#"
(*temporary) = "testing"

AddOns:
  Swatter, v5.20.5464 (RidiculousRockrat)
  DebugLib, v5.1.DEV.337(/embedded)
  GreenWall, v1.5.0-beta.1
  Stubby, v5.20.5464 (RidiculousRockrat)
  WIM, v3.6.18
  BlizRuntimeLib_enUS v5.4.8.50400 <us>
  (ck=c9)