AHT via Internet Recovery freezes...

Hello,

1) My system:

27" Imac mid 2011 (12,2)

3.1 GHz Intel Core i5

20 GB 1333 MHz DDR3

AMD Radeon HD 6970M 1024 MB

OS X Yosemite 10.10.2

2) I am suspecting a GPU failure because last night when playing a game, screen starting flashing in various colors making the game unplayable, but all other environments outside the game (when I quit it) were displaying fine. It appears as if the GPU overheated.

**Note that 3 months ago I replaced a failed GPU via Apple's HD6970M Replacement Program**

3) Because the issue is not persistent and a visit to the AppStore will probably be in vain, I would like to perform an Apple Hardware Test BUT:

- I am unable to find the recovery disk

- Pressing "D" does nothing, stating that AHT is not located within the HDD

- Pressing "Opt-D" prompts me to Internet Recovery -> connects via ethernet (also tried with Wi-Fi), then a few minutes after the process commences the "rotating globe" freezes, mouse cursor freezes, router activity lights stop, keyboard inputs freeze as well, and my only option left is a Hard Reset.

I am unable to find a downloadable AHT file anywhere.

Any help would be greatly appreciated.