What is this patch loop?
The patch loop is when your downloader downloads the new patch, but when you try to login to the game it prompts you that there is a patch avalible and please restart to download the patch.
What causes the patch loop?
The patch loop is caused by having the wrong client for your server installed, if you are playing on the Americas server it its normal client is the enUS, while other servers clients can connect to that server the wrong client will point to a different patch server, Asia needs the Asian client, EU needs enEU etc.
The patch loop can also occur if you have the enUS client but play on Asia/EU if there servers have not been updated yet or are still down for maintenance, remember all 3 regions do not have mainteniance at the same time, EU and Asia is after the US.
How do I tell which version of the client I have installed?
Go too C:\Games\Diablo III\Data_D3\PC\MPQs there will be a folder in there called en** (example enUS) this is your client, note that if you changed the default install location when you installed the game it will be different.
I bought the game in Australia/New Zealand and installed it so it should be the right client
This is true however I've found out that allot of stores sold 'grey import' copies of the game bought from Asia etc which while they work on any server the client they come with may not be the right client for your server.
I bought the game direct from blizzard and downloaded the client, clearly that should be the right client
Again an easy mistake, blizzard has a default client download, you have to manually change the download to the right client.
Well how do I get the right client then?
There is 2 options for you either:
Just go to battle.net and login to your account, on the summery page you will see Diablo 3, click it and go to Install/Re-Install the client. It will then bring you to the download page where you may have to verify your date of birth to access the Diablo download.
Now for the important bit, look here: http://users.on.net/~link22/Diablo/loop01.jpg click this to bring up your download options http://users.on.net/~link22/Diablo/loop02.jpg and select the client for your server(enUS for Americas, enEU for EU, Asia for Asia) then press save and then download the client.
Uninstall your old client and install the newly downloaded client and you will not see the patch loop again.
The other option is to change your client patch links so that it now connects to the US, this is done by(Mac users see the bottom of this post:
1. Open the file C:\ProgramData\Battle.net\Agent\agent.db (in wordpad)
2. Change all references of http://enSG.patch.battle.net:1119/patch to http://enUS.patch.battle.net:1119/patch (there will be 3, then save and close)
3. Run game client
How do I Uninstall my old client?
In windows 7 simply go to My Computer then up the top press 'Uninstall or change a program' find diablo 3 in the list and hit 'Uninstall/Change'
If you are having this issue on a Mac and want to change the agent.db file please follow these instructions:
1. Open Terminal.
2. On Terminal, navigate to your Diablo III folder by typing the following:
cd "/Applications/Diablo III"
(If you did not install it on the default location, type the correct path.)
3. Make a backup copy of the original .agent.db file first. On terminal, type:
cp .agent.db dotAgent.db.bak
4. Still on Terminal, type the following command to open .agent.db on TextEdit:
open -a TextEdit .agent.db
5. find the "patch_url" line and change its value to:
Obs: Do not remove any of the quotes or comas. Change the patch_url and nothing else.
6. Save and close the file. (If asked to unlock the file, do it.)
7. Now go in the Battle.net folder: (Using Finder. You don'tt need to use terminal anymore)
8. Once inside the Battle.net folder, select and move the Agent folder to trash. (don't skip this step)
9. Start the Launcher.