Why has my Mini-Display port stopped recognizing DVI monitors- Except Apple cinima displays?

I was having some video problems with my machine.

Took it in to Genius Bar, They sent it off for repair. Got it back the glitches on laptop display, however, my external display spazzed-- a few times: went to snow. Then a few days later it no longer recognizes the display (Hannspree 225HF) tried all sorts of power cycling's, connection/power order pairs, battery vs plugged in. NO DICE.

So. Took it back-they sent it off, I got it back, still NO DICE.

TOOK IT BACK A 3RD TIME- the guy plugs it into a nice 27" Cinema Display and WOW! BEAUTIFUL! He ran some diagnostics- says everything checks out.

NOW, HERE's THE RUB:😟

I get it back home: still no go; I connect it to my Gateway FPD1769 TFT display:NO GO.

BUT: They (monitors) both work fine on my Dell Desktop and Laptop running Win7-64ULT on DT and Win7-32ULT on Laptop. 😕

Does ANYBODY know what's goin on? I've tried different dongles too--

My Specs:

System Software Overview:

System Version: Mac OS X 10.7.3 (11D50)

Kernel Version: Darwin 11.3.0

Boot Volume: Macintosh HD

Boot Mode: Normal

Computer Name: xxxxxxx

User Name: xxxxxxxxxx

Secure Virtual Memory: Enabled

64-bit Kernel and Extensions: Yes

Hardware Overview:

Model Name: MacBook Air

Model Identifier: MacBookAir3,1

Processor Name: Intel Core 2 Duo

Processor Speed: 1.4 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 3 MB

Memory: 2 GB

Bus Speed: 800 MHz

Boot ROM Version: MBA31.0061.B07

SMC Version (system): 1.67f4

Serial Number (system): C02DWCFNDDQX

Hardware UUID: xxxxxxxxxxxxxx

------------

NVIDIA GeForce 320M:

Chipset Model: NVIDIA GeForce 320M

Type: GPU

Bus: PCI

VRAM (Total): 256 MB

Vendor: NVIDIA (0x10de)

Device ID: 0x08a2

Revision ID: 0x00a2

ROM Revision: 3571

Displays:

Color LCD:

Resolution: 1366 x 768

Pixel Depth: 32-Bit Color (ARGB8888)

Main Display: Yes

Mirror: Off

Online: Yes

Built-In: Yes

Connection Type: DisplayPort

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Thanks for any help or useful conjecture even.

BTW: This is not my 1st Mac "Rodeo"

Kind Thanks JBD

I'm going to sleep now, I'll check back tommorow to see if anybody has any ideas, Thanks again!