A point in the right direction. Re reverting to Mountain Lion.

1. Repartition and erase your hard drive.
2. Reinstall Mountain Lion.

If your computer shipped with Lion or Mountain Lion pre-installed:

Install Mavericks, Lion/Mountain Lion Using Internet Recovery

Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.

Boot to the Internet Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.

Partition and Format the hard drive:

1. Select Disk Utility from the main menu and click on the Continue button.

2. After DU loads select your newly installed hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed. Quit DU and return to the main menu.

Reinstall Lion/Mountain Lion. Mavericks: Select Reinstall Lion/Mountain Lion, Mavericks and click on the Install button. Be sure to select the correct drive to use if you have more than one.

Note: You will need an active Internet connection. I suggest using Ethernet

if possible because it is three times faster than wireless.

This should restore the version of OS X originally pre-installed on the computer.

1. back up everything

2. boot from eternal drive

3. format internal drive

4. install ML ( since i never had ML i am not certain whether you had a downloaded installer file or DVD or ???)

Either use migration assistant to copy files back or copy them back manually.

I know of no way to install an older system over a newer one.

I have 3 machines, all 10.9, wifi works great on all of them with 3 different routers, plus everywhre i go. fix your problem - its likely easier.

Grant

No, it won't. Do this instead.

Clean Install of Snow Leopard

Be sure to make a backup first because the following procedure will erase

the drive and everything on it.

1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.

2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported), then click on the Apply button.

3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.

4. When the installation has completed your computer will Restart into the Setup

Assistant. Be sure you configure your initial admin account with the exact same

username and password that you used on your old drive. After you finish Setup

Assistant will complete the installation after which you will be running a fresh

install of OS X. You can now begin the update process by opening Software

Update and installing all recommended updates to bring your installation current.

Download and install Mac OS X 10.6.8 Update Combo v1.1.

You can then redownload and install Mountain Lion.

I thnik Kappy has some more detail below. I'm not quite sure what he's saying is different, except that i guess oyu need to install Snow Leopard and then upgrade to ML ( makes sense).

The Snow leopard install DVD (original from your mac) in this case will be your startup disk.

I would still just fix what you have.

Grant

have you performed a re-insatll of OSX 10.9 over the copy you have now?

All i am saying is that there is no wifi issue inherent in 10.9.x that i have noted, so *smething* must either be:

1. corrupted --> re-install

2. misconfigured --> i will assume you have been through this

3. interfering --> eliminate any questionable, constantly running 3rd party software ( virus, networking especially)

Aside from that you will need to basically start over. That means ( and i will again keep this short and simple so as not to overwhelm):

1. back everything up because you will erase it and you will need it

2. start up your machine from something with OSX on it - either an installer DVD or an external drive that is a clone of your current drive (test it first!). The basic issue is that you will be erasing (formatting) your internal drive so you dont have an OS.

3. format your internal drive

4. install Snow leopard

5. put all your files, libraries back, hopefulyl with setup assistant

6. upgrade to ML

Which step is not clear? You might want some help?

Grant

Grant Lenahan wrote:

Either use migration assistant to copy files back or copy them back manually.

I think trying to use Migration assistant in reverse will not be successful. I have tried it and had major problems with Mail.

Sure, that's fine. I do charge double time on weekends and holidays, however. 😝

Yes, based on kappy's advice i suggested setup assistant.

I'm old school; i move files by hand.

Grant

It will work but only if it is not a mixed backup - part old system and part new. That just an accident waiting to happen. It must be a full old system only in order to work. Preferably, a completely separate backup.

Not sure what you mean Kappy. I upgraded to 10.9, (had 2 x full disk utility cloned 10.8 backups that I migrated from). All was well with 10.9 except for this. So I installed 10.8 on an internal and used MA to get me back to where I was. Mail refused to run correctly, I didn't get as far as trying any other iApps.

I just copied back the clone in the end.

As far as I'm concerned the most important thing you can do is have a bootable cloned backup, (or two).