Ubuntu always starts fine for me but after a while the text will start to corrupt to the point I cannot read it in the applications I am running and the purple background is pixelated into big squares. Obviously I can read the text on the browser but the text is corrupt in and from the url and google windows up.
Possibly, this is a form of a known bug. If indeed, then it will not manifest in Ubuntu 2D. Try to log out and choose 2D as your session; do you still experience the same problem?
If not, then your problem is related to compiz. Compiz in 12.04 has several bugs. I had to install an older version of Compiz from a PPA; the instructions are here. However, as a word of warning, some people report that they still have your problem ("white menues") even when using this compiz version; see comment #144 here.
To change to Unity 2D, logout and when you get to the login screen click on the Ubuntu logo at the top of the panel, just to the right of your login name. Select Unity 2D from the drop down menu then type your password and continue with the login. If you get the password wrong you will have to re-select Unity 2D from the drop down as it will reset back to the previous default.