Some DVDs dont work, some do. Whats the problem?

[Nipun]

I have recently purchased Portal 2 and Crysis 2 from flipkart. I received Portal 2 yesterday, which didn't work. On return of Portal 2, I got a new Portal 2 disk and also received Crysis 2 which I ordered. When I insert the disk(any of them), computer works normally(when I refresh on desktop, it does that normally). But, when I try to open My Computer, it doesn't open. When I make a few more clicks, and hover my pointer over taskbar, it shows busy sign, and nothing happens! I am even unable to shut down the computer, so everytime I just have to unplug directly. When I take the disk out and restart(unplug then turn power on), it works normally.
This only happens for 3 disks(2 of portal and 1 of crysis), but all other disks run fine on it. What could be problem? I am really frustrated by Flipkart!!!

(NOTE)EDIT:
I inserted the disk, opened My Computer, and computer hanged as usual. I restarted button(power button), without taking disk out. This time it showed the disk. Can this be a problem of DVD Writer(or reader-whatever!)?

[MatchBoxx]

Which OS do you use?

[Nipun]

Windows 7. And the Portal 2 worked perfect when I inserted it, which wasn't working last time. The issue fixed automatically

[MatchBoxx]

The old DVD writers do give problems overtime...is yours a old one? My Dual Layer Digit dvds hangs up the system b'coz of the old writer

[Nipun]

Its just a week old..... And probably its not Writers fault, now I think() as when kept inserted and restarted, it worked. Next, Portal 2 also worked without a reboot(which earlier wan't!). I doubt that its the Optical Drive troubling. But, now since they all are working, its fine for me. Thanks for help though