Resolved Monitor blanks momentarily, then restores

My Dell 19" LCD monitor (E198WFP) will sometimes go blank for several seconds. It happens at odd times, and I can't say I'm always doing the same thing, but typically when I'm on the internet (latest version of Firefox). I downloaded the latest drivers for the integrated graphics (Radeon HD4200), and checked for the latest monitor drivers. I don't use a screen saver, and when the screen blanks, I don't see the message from the monitor telling me that it is going into power save mode. I'm willing to install a graphics card, but the choice is overwhelming. I don't want to spend money and wind up with less than I have. I am not a gamer, but do a lot of photo editing. Any suggestions will be appreciated. I'm running 64-bit Win7 Home Premium.

 

I checked the refresh rate and found that the video driver and monitor didn't match. Once I changed the monitor, the blanking has ceased. Thanks for pointing me in the right direction.