As I'm sure you're aware Minecraft has now been updated to 1.5
For the time being the server will continue to run 1.4.7 until we are able to update, this means that if you update your client version to 1.5 you will receive an Outdated Server error when trying to connect to MCA.

You can rectify this by following the steps below that were written by Yennage and ekover97 for previous version rollbacks, these instructions are for Windows and Mac users only.

Instructions for Windows (Thanks to Yennage)
Step 1: Download the 1.4.7 jar from here, this jar is 100% vanilla meaning that you will need to reinstall any mods you were using again.

Step 2: Open up the %APPDATA% folder. You can do this by hitting Windows Key + R to bring up the Run box. Then simply type in %APPDATA% and click the Open button to get to the folder.

Step 3: In AppData you should see a folder at the top called .minecraft, double click it to open it. As a quick bit of info, this is where MC stores all your singleplayer saves etc. if you ever need access to them

Step 4: You should see a folder called bin, double click it to go into it (this is where the minecraft jars are stored).

Step 5: You should see a file in here called minecraft.jar (if you updated, this is the Minecraft 1.5 jar) rename it to something like minecraft1.5 (alternatively you could just delete it, but renaming allows you to switch back at will)

Step 6: Copy the 1.4.7 jar you downloaded in step 1 into the bin folder.

Step 7: You should now be able to restart minecraft (Be sure to click Not Now if asked to update) and be able to connect to the server as normal.

To switch back to 1.5 just go to the folder and rename minecraft.jar to minecraft1.4.7 and then rename minecraft1.5 back to just minecraft, then restart MC.
You may also want to use MagicLauncher to organise your jar files and launch the version of any jar file you own.

Instructions for Macs (Thanks to ekover97):

1.Download a copy of the version 1.4.7 minecraft.jar here
2. Move that file to your desktop
3. Follow this path to get to your Minecraft files: Finder>(Your Username)>Library>Application Support>minecraft>bin NOTICE: If you have Mac OS X Lion, your library might be hidden.
4. Rename your current minecraft.jar to minecraft1-5.jar
5. Drag the new downloaded minecraft.jar into your bin folder.
6. Exit out of Finder, open your Minecraft, and it should work. To switch back, just name your minecraft.jar to minecraft1-4-7.jar and your minecraft1-5.jar to minecraft.jar, then run minecraft again. While you're doing all this, be sure to EXIT OUT of Minecraft.

We're working hard to to get things together for an update. As we rely on bukkit and other plugin developers we're waiting for them to release stable builds for 1.5, our ETA for an update is therefore unknown.
We only run development builds unless they're tried and tested for hours beforehand and they work as we expect them to.
Feel free to discuss this in the community talk thread: HERE

See you around,
Minecraft Addicts Staff.