Details:

• Dual 25" monitors connected to HP Envy via HDMI and display port via DVI adapter.
• Power scheme is set up in high performance (Dim Display: Never - Turn Off Display: 15 mins - Computer Sleep: Never)
• Screensaver is set up to kick in after 10 mins of idle (which happens)
• 5 minutes later, the screensaver stops. The "Monitor Going to Sleep" notice appears on screen and monitors go to sleep briefly. All is well thus far.
• Suddenly, the Windows 7 alert sound when a device is unplugged is heard.
• Monitors then turn back on. Screens are black. Only the mouse cursor is displayed. Backlighting is back on.

This only started happening after I obtained and connected the second 25" monitor a few days ago. However, I had a 24" in its place before, and this wasn't happening.

Why is this happening and how do I correct this behavior?

Thanks in advance.