Hi
keshav3766 -
I faced the same problem few weeks back when I upgraded to Mac OS from windows. Apparently, all the IP addresses didn't allow access to mba.com, the websites from both the laptops were taking forever to open. I tried using hotspot from my mobile - but in vain! I opened the website via phone on iOS, that was accessible however, I was not able to download the GMAT prep software.
I asked a friend of mine, to download the software from mba.com and send it via google docs and it worked. Sorry, can't help you much, I am still unable to download the GMATprep software. Should you need GMAT Prep for MAC, do let me know I still have it on my email - Just pm me.
Hope this helps.
Anubhav