MacBook Pro (early 2011) suddenly stopped showing on external display

Hi All. Please see below. I tried to be as clear and concise as possible. Let me know if I need to clarify or elaborate on anything. Any insight appreciated. Cheers.

Issue
MBP no longer detecting external display.
Worked fine for almost a year and then suddenly stopped.
Prior to it going, I noticed some flickering with the screen that required some readjustment of the MiniDisplay Port to get it to stop.
No recent Thunderbolt firmware updates.

What I'm working with:
Computer
MacBook Pro (early 2011)
OS: 10.8.5
Memory: 16GB 1333MHz DDR3
Processor: 2.3GHz Intel Core i5
Graphics: Intel HD Graphics 3000 512MB

External Display
DELL UltraSharp 2209WA 22" IPS WIDE LCD (supports DVI)

MiniDisplay Port
Monoprice DVI to Thunderbolt adaptor


What I've tried
1. Reset the Mac's parameter RAM
2. Unplug external display + Plug external connector to MBP + plug in external display again.
3. Hold the "Option" key while in System Preferences/Displays and clicking "Detect Displays"
4. Downloaded GFX Card Status. Tried plugging in external on "Integrated", "Discrete", and "Dynamic".
5. Unchecked Mirror Display [ ] - THEN plugged in external - THEN checked Mirrory Display [ √ ] in System Preferences/Displays.

I've read through these threads which is where I got advice on what to try:
https://discussions.apple.com/thread/3350132?start=0&tstart=0
https://discussions.apple.com/message/16743362#16743362

Results
Option #5 worked once for me yesterday, then it went back to not working and hasn't worked since.

The nearest Genius Bar to me is a 90 minute one-way drive so I'm using that as a last resort.

Could it be that my DVI/Thunderbolt adaptor needs replacing or is it possible that my Thunderbolt port is damaged? Though it could be, I don't see this as being an issue with the external display because I've read so many other similar instances with MBP owners.

Thanks for reading.

mr.cotton said:

...
Prior to it going, I noticed some flickering with the screen that required some readjustment of the MiniDisplay Port to get it to stop.
....

Click to expand...

Prime indication the adapter should be replaced.
After unplugging everything and plugging it all back in - the next thing to try is a different adapter/cable.
And/Or, trying to connect to a different monitor/TV.

Don't know why - but, for the past 10 years or so, video adapters just seem to fail more often than they should be.

Thank you for the quick, concise reply Bob.

I had a hunch that the adaptor may be the issue but had a hard time believing that in less than a year with zero wear and tear it could already be showing signs. Suppose that's what happens when one goes with an off-brand.

I'll pay the extra $20 this time for the Apple adaptor and see what happens. I'll be sure to post the results for others with similar issues. Cheers.

Got the adaptor in the mail today and that was indeed the issue. What threw me for a loop was that it started working again after I tried #5 in my original post. Also, the fact that I had the original adaptor for less than a year and had not moved it, dropped anything on it, etc. once during that entire time.

For those interested, I decided to purchase an off-brand on Amazon. It was $6 (Prime) and 1/5 the cost of an Apple adaptor.