I just opened the launcher up to set the options in-game. I set my resolution to 1920x1080 (my native res) and the monitor went into power-save mode. I was able to alt-tab out of the game, and the monitor came back, but evey time I went to the game window, it went to power-save mode.
I'm using the latest ATI drivers for my Radeon HD 4890, and I'm able to run other games at 1920x1080 without a problem.
Right click on yoru desktop and go to properties. click the power saving option (usually found under screensaver options, and set everything to a high value, or to never. The latter choice being the most preferable)
This should remove any issues you are having. If power saving mode is still happening after this, you could try reinstalling your graphics drivers, as you may have a broken/crossed install, that STO is flagging up.
The driver re-install may work, but this is a fresh copy of Windows 7 Home Premium, with the latest drviers. I installed the OS after the drivers came out, so there's only been 1 install of the video drivers. More then likely it IS the car/drivers, however, all my other games present no problems.