I have experienced the same exact issue since day one of completing my build and have yet to determine the problem. As others have said, the problem is intermittent and has been very difficult to troubleshoot. Thin white or black flickering lines will appear at the top edge of the screen. These lines will also appear when I open new windows. I've noticed black and white backgrounds seem to intensify the problem. A restart temporarily fixes the problem, but it always returns. So far I have done the following:
1. Used 3 different monitors and a television.
2. Used VGA, DVI, and HDMI ports and different cables for each.
3. Ran a memory test to check for errors at both default timings of motherboard and optimized timings 8-8-8-24. (Showed no errors)
4. RMA my A8-3850 and replaced it with a new one.
5. Monitored temperatures (APU runs between 27-30 C, Motherboard runs between 29-31 C.
6. Updated Catalyst Drivers to newest version over the course of a year. (No change)
7. Updated Bios to newest version multiple times for motherboard. (No change)
8. I've both set in Bios the UMA Buffer Size, which sets aside amount of RAM to dedicate to GPU portion of APU, to Auto and to a custom size. (No effect)
9. Changed Windows Power Settings from Balanced to High Performance. (No effect)
To be honest, I've always suspected an issue with the ports on my motherboard. Some sort of defect. Mainly based on the fact both a screenshot and video recording software failed to document the flickering lines. It seems the only common ground we all have is an A Series AMD APU. Everyone has different system configurations and HP laptop owners are experiencing the same issue, I am leaning back towards a graphics driver problem. I recommend reporting the problem to AMD using this form at http://www.amdsurveys.com/se.ashx?s=5A1E27D20B2F3EAC
AMD A8-2850 APU Processor
G.SKILL Ripjaws X Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Memory
COOLER MASTER Silent Pro M600 RS-600-AMBA-D3 600W ATX12V V2.3 Power-supply
ASUS F1A75-M PRO FM1 AMD A75 Motherboard
Corsair Force Series GT CSSD-F120GBGT-BK 2.5" 120GB SATA III SSD
Seagate ST3500418AS 500GB ATA HD
Samsung TSSTcorp CDDVDW SH-S223C ATA