WowAce

What steps will reproduce the problem?
1. This issue seems really hard to reproduce.  It was originally reported to me as a conflict between SatrinaBuffFrames and ShamanFriend, but just running the two addons doesn't reproduce it.  I have found the following to work to reproduce it.
2. Install Real UI (http://www.wowinterface.com/downloads/info16068-RealUI.html)
3. Install Shaman Friend (2.31-r34 http://wow.curse.com/downloads/wow-addons/details/shaman-friend/download/541444.aspx).

What is the expected output? What do you see instead?
No LUA errors.
LUA errors and Satrina Buff Frames fails to function.

What version of the product are you using?
1036 and 1037 have the issue.

Do you have an error log of what happened?
Errors look like this:

1x table: 11D2CD28
nil

Locals:
nil

1x table: 1950F328
nil

Locals:
nil

Please provide any additional information below.

If I downgrade ShamanFriend's AceAddon-3.0 to the version in 1035 the issue goes away.  If I upgrade all addons libraries to 1037 the issue goes away (actually just replacing the AceAddon-3.0 in the first addon loaded also works, I tried it).
The issue seems to be when most addons use the old AceAddon-3.0, but then an addon loaded later uses AceAddon-3.0 1036/1037.

If there is something addons need to do to work with the change to AceAddon-3.0 in 1036 or a way this issue can be worked around, please document it.  I do not know the best solution for this issue, I am debating rolling back ShamanFriend's Ace3 library to the 1032 release.

The following change in AceAddon-3.0.lua from my testing is the cause of this issue:

local function onEvent(this, event, arg1)
	if event == "ADDON_LOADED" or event == "PLAYER_LOGIN" then

to:

local function onEvent(this, event, arg1)
	-- 2011-08-17 nevcairiel - ignore the load event of Blizzard_DebugTools, so a potential startup error isn't swallowed up
	if (event == "ADDON_LOADED"  and arg1 ~= "Blizzard_DebugTools") or event == "PLAYER_LOGIN" then

From my experience, this issue is caused when addons attempt to use functions with the same names as those embedded by Ace-Addon-3.0. For example:

http://wow.curseforge.com/addons/sunn-viewport-art/tickets/27-library-conflicts/ http://wow.curseforge.com/addons/gnosis/tickets/17-ace3-versioning-issues-solution-found/

The single change to exclude Blizzard_DebugTools isn't what is causing this. Versioning and version upgrades are.

Cybeloras, I had assumed that:

local MAJOR, MINOR = "AceAddon-3.0", 10

to:

local MAJOR, MINOR = "AceAddon-3.0", 11

was not the source of the problem. That is the other change in Ace-Addon-3.0. It sounds like from past issues you believe what is causing this issue.

As Cyberloras said, its most likely not a problem with AceAddon, rather a problem with an addon having a function with the same name as one in AceAddon, causing that function to be over-written on library upgrade.

It would also help alot if you actually posted a proper Lua error message, instead of that odd things above.

Nevcairiel, those are the actual lua error messages that appear in game. They are totally useless error messages at least to me, but those are the errors WoW gives.

I can produce this error by upgrading the AceAddon in another addon without ShamanFriend being loaded at all (as long as the first addon loaded is not the one upgraded as that causes the error to go away).

Is Satrina Buff Frames the only addon that fails to function?

I can produce the table nil error without Satrina Buff Frames, but so far that's the only addon I've found that actually breaks and stops working.