My work PC was upgraded by the tech guys (RAM only) and ever since my screen has been flickering but they do not know why this has happened and have yet to fix it. Does anyone have any ideas as to the problem as using the PC is causing me to get headaches and hurting my eyes!
Check to see if the monitor cable is correctly seated on both ends. Check for damage to any pins on the monitor cable. Assuming you don't have onboard video, you may also want to have the IT people check to see that the video card is correctly seated and that all of its internal cables are connected correctly.
I wouldn't think that a ram upgrade would cause video flickering, though if it is an integrated graphics chip it might since that would share system ram. If that is the case, maybe it is the wrong type of ram for the computer, they have different speeds that they run at and usually the faster one downclocks to match the slower one, but it's possible that it could cause problems.
Maybe for a start you could check to see what the old and the new ram are and see if they match, then maybe try each one individually and see if you still have a problem, if your old one works fine and the new one flickers, then it's probably a bad stick of ram. If they both work on their own and they match, maybe you are overloading your motherboard with too much ram.
It's possible that a Electro Static Discharge occurred by the dude working on your memory that's caused a little bit of damage to your video card. That's kind of rare, but it can happen. I'd actually try using a different monitor for a little, maybe switch with a coworker for the day? Alternatively, if you could replace your video card, that'd help. Of course, before doing any of this, you may wanna make sure your cables are all connected tight.
It doesn't sound like a software problem, but never say never.. You could toy with running on a Live Linux CD for a bit, if it does it while on that, then it's at least definitely hardware.
Heck, maybe your cell phone's causing some interference??
Anyway, just isolate and rule-out stuff.. That's the only way in my books.