I have this problem with my Mac, too. I think you should wait a bit until everything is in order again. Note that Boot Camp drivers for Windows 8 may not be uploaded to the server yet, so you will have to wait.
However, I have discovered that OS X 10.8.3 limits Windows 8 to some new Macs only, and old Macs can only use Windows 7. However, as it looks like you have a new Mac, this shouldn't affect to you
I have a MacBook Pro 13-inch, Early 2011, and have upgraded to OS X 10.8.3. I attempted to install Windows 8 via the "Boot Camp Assistant" utility application, and received the "Your Mac only supports Windows 7" message when attempting to "download the latest Window support software from Apple."
According to this Apple support article, the early 2011 13-inch MacBook Pro should be capable of running Windows 8 (64-bit) with Boot Camp 5:http://support.apple.com/kb/HT5634
Apparently this is a glitch in the Boot Camp Assistant, as I've read of it affecting even newer MacBooks. With the "Your Mac only supports Windows 7" message, I was uncertain that Boot Camp Assistant would download the correct set of drivers for use with Windows 8. Instead I went to this page: http://support.apple.com/kb/DL1638 and downloaded the Boot Camp Support Software there. I followed the directions to copy the contents of the downloaded .zip file to the USB flash drive. Then I used Boot Camp Assistant to install Windows 8 after deselecting the "Download the latest Window support software from Apple" option. After Windows 8 was installed and opened then I opened the Boot Camp folder on the USB drive and double clicked on "setup.exe". Windows 8 has since performed flawlessly on my MacBook Pro, so I believe this to be a suitable work around. Hopefully Apple will soon correct the flaw in the Boot Camp Assistant.
Download and extract the bootcamp 5.0.5033.zip
Unpack and copy the extracted file onto the windows desktop.
got to start > programs > accessories > cmd prompt (run as administrator)
....now highlight only the selection, then right or cmd + click and run as administrator (note: if you cannot right click, you can also highlight the selection and press shift+F10 to bring up the context menu).
In the cmd box navigate to the bootcamp folder on the desktop, will be something like this:
cd Desktop (press enter)
or if that doesn't work, then:
cd (your user name)
cd bootcamp5.0.5033 (whatever the bootcamp folder name is)
you can then type:
This will list the folder contents.
Once you are in the folder where you can see the bootcamp.msi file (note: you will probably only see the filename as bootcamp and 'type' as application in the windows environment) then type the following:
msiexec /i bootcamp.msi
This will launch the bootcamp application. It may look like it freezes when the nvidia drivers are installed, but be patient - it can take a few minutes until it gets through that and the progress bar did not progress on my installation.
Also, I've seen a few people offer up the 'troubleshoot mode' installation fix (you've probbly already come across this fix if you have found this post, so no point me covering that) which did not work for me. The above 'setup.exe' was not successful for me either.
A lot of posts bang on about running the 'bootcamp64.msi' file, though seeing as this version of bootcamp only runs 64 bit software, there's no reason to call it 'x64' - hence, it's only 'bootcamp'.
I ran this fine on a Mid 2008 15" MBP A1226
The only thing I need now is to see if I can fix the key mapping... is there an app like 'MagicPrefs' I can run in the windows environment that anyone can suggest? (Running a UK machine with a US keyboard - long story).