I have and HD 5450 (Powercolor AX5450 1GBK3-SH).
It's in a Shuttle cube (SZ77r5) with an i7-3770.
I'm currently running windows 8.1, but this problem occured with Windows 8 as well.
Since I just upgraded to Windows 8.1, I tried out the new 13.9 driver. Once everything is up and running I have this issue where my secondary display will "drop" from my system momentarily. On the DVI-D i have a 27" Potalion korean monitor running at 2560x1440. My Secondary monitor is a Samsung SyncMaster E2220 at 1920x1080 connected to the VGA.
I believe I fixed this problem on Windows 8 by trying progressively older and older Catalyst builds, but I was hoping there's a fix I could do without using an old driver?