Problems in playing video - short squiggly lines appear randomly

Hi, I am not sure how to describe the issue so all my googling has been in vain, I hope you can help. I am not even sure which section to post, I assume it's hardware-related but maybe it's not.

I am running Win 7 with Asus p5K motherboard 4GB RAM NVIDIA GeForce 8500 GT.

Since yesterday (no new installs) when playing videos occasionally red or/and short squiggly lines appear for a few frames - kind of flash-like - and disappear. They return in different parts of the frame at irregular intervals. Could not make screens as in KMPlayer scrolling between single frames the lines appear to be inter frame (appear only on the scroll between two frames but in neither of the two).

I am also noticing a similar event, this time covering all the monitor screen which much longer lines, at boot. Specifically, after I input my password.

So far I have ascertained that:
1. it's not a problem with the files themselves - I am having the issue also with older files which I have already viewed without problems
2. it's not format related - I am having it with all the formats I tested: .avi, .mpg, .mp4, .flv
3. it's not player related: it's occurring with KMPlayer, Media Player Classic - Home Cinema and VLC portable which I just downloaded for a third option


I have attempted the following so far, without having any results:
1. rebooting
2. uninstalling all codecs and reinstalling the latest K-Lite Codec Pack
3. updating the NVIDIA drivers
4. checking device manager

As I mentioned, I have been unable to google for the problem, as all description I have come up with appear to produce unrelated hits.

 

Take a screen dump (snap) of your issue and post it here as attachment or provide a link to the image. In the meantime can you connect your system to another monitor. If on laptop external monitor. Are you talking about Onboard video graphics where your having the issue or adapter card?

Could be:

PSU is going on the way out
Onboard Graphics or your Graphics adapter on it's last legs

When you reboot the system or start-up the system do you see a flicker effect on the your monitor screen in the upper top blank screen?

 

I can't picture your problem, but just a shot in the dark. I 've heard about artefacts in video in cases of :

- Bad RAM.
- VGA card overheating.

RAM can be checked with Memtest or similar programs. VGA temperature with some other program (its own or maybe GPU-Z?).

 

hope this is ok, was intent in getting several points of view, rapidly

 

Turns out that the problem lies with the monitor.

I had totally forgotten (duh!!) to test my secondary monitor (I run a dual monitor system) and sure enough on it I had no problem playing various video files or at reboot.

Dell has arranged to substitute the faulty monitor (still in warranty) within 48 hours - fast procedure, hassle-free, so it appears that everything is solved.

Thanks to everybody for the help!