CS4 not updating changes

Hi there. As this seem to be a simple question I'll post it here on the basics.

I just upgraded my main machine and my software. Now I´m on vista 64, 8GB of RAM and photoshop CS4 64 (master collection).

Everything seems to be ok but one thing. (a damn annoying thing) Everytime I write something with the text tool or apply some correction nothing happens. I have to minimize PS or hit F and then it updates.

The weird thing is it was not happening on my PS installed on my laptop.(wich is way less powerfull)

I tryed disableing OpenGL since I´m an AE guy and that is a pain in there. Nothing happened.

So I kindly ask: Does anyone out there can show me something that would possibly set things back to normal?

Also, I´m running with all the latest updates.

Hope I made myself clear enough.

Big thanks in advance.

Cheers.

adriano.