Unable to validate core data files?

Technical Support
It seems to only be happening in act 2 for me so I don't know
I am getting the error and I am farming in act 1 butcher. What else should we do to fix this? >.<
Ugh...this is annoying. I couldn't even get in the game this time. I got that message trying to change quests.
I too received this error this morning for the first time. Act 1 omw to Leoric.

In hell, oh and I play HARDCORE! Not great when my screen minimizes with an error message! Please fix before something bad happens.

Oh and after the error, I pull back up D3 and me and my friend are both invisible but our auras are present. So I re-booted D3 and it was fine.

My computer and RAM is new - within 6 months and my video card was updated when D3 came out.
I'm having the same issue.
cant even play hardcore mode becuse if the error comes up i am dead it sucks its happening all the time 40 times every !@#$ing day, doing same quests all the time
...paid 67 dollars for a game i can't even play.. pretty pissed off at the nerf on ias now this bull!@#$..gg blizzard
Reinstalling for the 4th time is not an appropriate solution. How can a major company like Blizzard have so many issues with their client? I have never even experienced even close to HALF this many problems with another game.
Yeh I'll add my name to the throng of people suffering this one -_- yay....
Some details about this problem:

This "Diablo III was unable to validate core data files" error started to occur since I bought the game.
At 1st I thought I had some installation problems, so I re-installed the game.
That didn't helped.
After that I copied the fully working copy from my brother's lap top.
Fail again.
After a while I completely removed it from my PC, and installed it again.
Problem still present.
I deleted the folders in C:\Programdata\Blizzard Entertainment and C:\Programdata\Battle.net. Still not fixed...
What to do?
The bad thing is that the error pops up more often and sooner once I start the game then before!

P.S: I'm running it on a PC with Win 7 64-bit; DirectX 11; Intel(R) Core(TM)2 Duo CPU E4600 @ 2.40GHz 2.39 GHz with 4 GB RAM and a nVIDIA GeForce GTS 450 graphic card (more then suffice to run on recommended settings)

I've also been having this problem. I tried installing the game on two different hard drives. Re-installing the game seems to help for about a day or so, and then the problems come back at the same frequency.

I hope its something that is wrong on OUR side, so a fast fix can be done if found.
I have reformatted my computer from WIN7 ultimate to WIN7 professional and still the error exist. Can't find any other solution.
I don't know what to do at this point... It's better to farm Act 1 and Act 2 and I can't keep 5 stacks due to this error... I've tried every fix Blizzard has told me to try and nothing works... What's the deal man
This error could be triggered by a lot of things. If you guys are having problems elsewhere @ your PC too(i had), then it's time to start diagnosing/swapping your hardware. In my case a simple memory stick swap fixed all the chronic problems including this error, but if for ex. all of your dimm slots are faulty, then you're screwed and need to acquire a new mobo.

Data corruption, which this error is about, could be triggered by either your memory, HDD/SSD or even a faulty sata cable(insert more devices if you know), unless something else happened during the download. If a reinstall won't work, then you might have to start checking your pc's hardware for problems.
Many of your root cause will be different to mine but my error is a malware issue.
I found I was getting this error from a malware in datamngr.dll which came along with a searchqu toolbar which I don't even remember installing.

if you have this toolbar installed, don't uninstall with its uninstall executable.
that will uninstall the toolbar but attach more malware on to your computer.
i've manually removed all its registry and .dll files but for users in my situation can google an alternative way to uninstall it.
I'm getting the same problem here, I've tried everything & still get this error. Started happening after 1.0.3 patch so I know it's blizzards screw up.
I'm betting this error is only affecting a small portion of their player database so they don't bother rushing to fix it. it'll probably be until next patch before this issue is resolved...by then they'll probably only have ppl like this http://www.youtube.com/watch?v=LICrPuTybmU
Hey fellas just to let you all know im having the same problem and i have done the uninstall and the re install method and it still happens..... hopefully blizzard can fix a growing problem
i just got booted again while playing since my last post and this time it gave me an error code to use to communicate with blizzar.net here it is


hopefully that will help you blizzard!!!
I bought the game a month ago and it ran error free for the last few weeks. I encountered this problem today. For me the error is very regular and occurs at any time, sometimes at start up, sometimes in gameplay... I can't even run the game for 5mins

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