I've upgraded my Windows 8 machine to 8.1 Preview, and almost everything seems working perfectly. The only serious issue is that after some minutes or hours (unpredictable) of usage the text color switches to the background color as you can see on this screenshot:

On this image I searched for "exp" in the Search charm and from the selection you can see that it auto-completed to "explorer" and returned the related search results. So the UI works and responsive, but unreadable.

The same happens in other places as well, for example most text in the PC Settings dialogs are also invisible (and thus unusable). The issue affects only modern UIs, not any classic window and dialog.

I cannot reproduce the issue at will, but it can be fixed by signing out and signing in again. The video driver is for ATI Mobility Radeon X1600 from AMD which worked well with Windows 8 before the update.

Thanks for fixing it in the RTM version.

- Gyrgy Balssy

Try download and install the latest graphic card driver for your PC.

What is the model and manufacturer of your PC?

It's a Toshiba Satellite A100-237 laptop with an ATI Mobility Radeon X1600 graphics card.

I downloaded the latest drivers which is lageacy driver that works like a charm in Windows 7 and in Windows 8 RTM, but not in the 8.1 Preview.

Thank you for reporting this issue, please post it in Toshiba forum.

Also, try uninstall the driver and restart your PC and run Windows Update and check if it will appears through Windows Update or not?