I tried messing around with my phone for a while and seeing if i could get anything to work, i realized that i had downloaded the handcent sms app instead of using my original text messaging but that didn't make a difference at all. And i saw the video that you posted PyroSporker , and believe i downloaded the same exact drawing app that you used in your video ( at least i think so ) and as your phone left out parts of the line where your screen you said was unresponsive or dead in those areas. My phone didn't just not draw the line in those spots but instead will jump over to the right or left depending how close or far away from the right edge of the screen i am. And drawing a straight line up and down it will basically zig zag straight lines to the left and right at different angles
I have attached a picture that i stupidly drew in paint of pretty damn close to identically what my screen looks like in the drawing app and yours from the video
as you can see to the left of where my screen seems to have the problems is pretty much fine and where the lines zig zag between the two straight lines i drew my fingers up and down and it kept shooting those patterns in between the lines.
any comments or advice would really help !
thanks
Welcome to the forums. I just wanted to clarify that it is not my video, I ran across it on Youtube and I posted it here to help others visualize what is taking place on some handsets. I have not had touch screen issues myself but found it so very curious and took an opportunity to provide some visual proof and further exemplify this issue for everyone's sake. It is a tough thing to try to describe to others, so a video really helps others to understand what could be going on.
Your MS Paint skills are quite impressive

For future reference, if you want to take a screen shot of what is displayed on your phone's screen all you have to do is hold the power button and hit the home key. It will save a screen shot to your pictures folder
(you must have the most recent major OTA - Over The Air - software upgrade installed and be on Sprint. Last I read, the non-US version of the Evo 3D did not have this feature)
Your symptoms look very much like a phone with a faulty digitizer rather than a multi-touch issue (this threads topic is multi touch issues - but they are similar and can be co-related). The Digitizer is the touch receptive substrate that interprets electrical touches to the phones display surface which are actively translated and computed by a chip on the system board. If you didn't look at the topic I linked in post
#4 you should since I believe it is a bit more applicable to your case.
Ctenorman has given you some great advice. Your first step is to backup the things you would like to save and then perform a factory reset. A factory reset could possibly remedy a software clog and fix the problem. If a factory reset does not work however, if this is a deeper issue or hardware malfunction your best bet will be to get a replacement handset.
Root once you have a stable phone and are ready to experiment, the choice is in your hands.
Inside the People application, if you press the menu key you will see a Import/Export tool that can export your contacts to your MicroSD card. Or if you are feeling saucy you can back them up to your Gmail account (I don't like too much personal info stored there, but to each his own).
I also recommend
SMS Backup and Restore on the Market. It is relatively secure and exports your text messages to your SD card in a universal format that can easily be imported back without issue.
As far as Applications and Settings go I like to start fresh and restore/reinstall the essentials one at a time to monitor any conflicts or issues that could occur. I run a lean system and try to keep things simple to avoid software conflicts.
Your SD card will not be wiped unless you tell it to be. Keep a computer back up just in case the inevitable happens. It can also help sometimes to physically remove it from the phone before the reset and re-install it once the reset has occurred and you are running clear again. Take it out of the equation to limit the possibilities. It is also a good opportunity to go through your SD card on the computer and clear out any erroneous files and folders.
Good luck, Hope you get the underlying cause figured out. Post back and let us know how things go.
P.S. Just to double check, Do you have a screen protector or case installed that touches the active display surface?