During a Ubuntu 12.04 install your screen may go blank (purple) part way during the installation process. For me, this always came directly after setting my hostname.
The likely fix is to run the installation with nomodeset option. For details see the How to set NOMODESET option discussion. The short version looks like this:
- From the Ubuntu menu > F6 > Select nomodeset
- From the Ubuntu menu > Install Unbuntu
Hopefully the rest of the install process is uneventful.