my macbook pro does not detect external display anymore

I had the same problem, tried all the above... got very frustrated... then discovered somthing called parameter RAM. if you clear it, your monitor connects fine again!

• shut down computer
• press power button to turn on the computer
• immediatly, before the grey screen appears, press and hold command + option + P + R. hold the keys down until the machine restarts and you hear a second startup sound...

no guarantees, but it worked for me

By coincidence I discovered the following.

After installing Mountain lion on my macbook pro 2.53 Ghz intel core 2 duo, I could not connect my Apple cinema anymore. Going back to Snow Leopard did also not work.

I tried everything out that was already mentioned in this blog.

But, I can still connect to my beamer. But not with an other external display (I used the same connector)

How come? I think it is the responsibility of Apple to fix this problem. So Apple fix it asap

But if Apple keeps silent about this issue, I hope some of the readers can help.

I had been using an external monitor on my macbook for months. all of a sudden a couple of months ago it stopped working. The monitor is fine, I tried a new Apple adaptor yesterday to see if that was the issue. Went through most of the trouble shooting mentioned her that I could do and ended up wasting HOURS trying to get the darn thing to work again.

Went I plug it in the screen on the macbook turns blue, flickers a bot so that i can see the desktop, then turns solid blue again and just keeps doing this until i unplug the cable..... The monitor is detected and when Display pref is open it even knows what model is hooked up.....

Is there an easy solution yet?

Lion 10.7.5 same problem here!. DVI to VGA doesn't work, DVI to HDMI works. I can't believe that this problem hasn't been solved yet.

I had this problem about a month or two ago. Just read the past few pages. I tried EVERY single solution listed and nothing worked. I upgraded to lion, downgraded back to snow leopard, I tried all the tricks of plugging and unplugging etc etc. And the only thing that worked was buying a brand new vga to mini display adaptor. As soon as I plugged it in, voila! Worked perfectly fine.

Would it be a good idea to go to the genius bar? Has someone tried it?

I've tried everything, even several brand new DVI to VGA adapters.

I was having this problem and sanctionone's soultion posted January 4th worked for me. Late 2011 MBP, HP monitor, Best Buy DVI->HDMI cable.

Not sure that happened but all of a sudden my HP ZR2440w is not working with my MBP? This setup has been working fine for almost a year and not is not. When I plug the monitor in the MBP is not seeing it and trying to set it up. If for some reason it does notice it all is well for a for a while but if the MBP goes to sleep apon waking up the external monitor does not wake and the MBP stays as the second monitor and does not switch back to the main monitor. At this point I'm stuck because even if I unplug the external monitor the MBP never switches to the main monitor so I have to do a hard reboot which is never a good thing. What's up with this?

Interesting the number of "stand in the corner on one leg with your right finger in your left ear" type answers there are here. This is yet another major bug in osx. Apple is a major corporation and basically it lacks a captain since Steve Jobs died. There are a few workarounds to this, on my wife's macbook pro it means a reboot any time we need to connect a projector. If you are in a position to, visit your local Apple Store and complain, otherwise email Apple and complain. We are all dependent on Apple, some more so than others, and it is not acceptable that they are foisting a buggy OS on us (this would be less of an issue if we were allowed to continue using older versions of OSX but Apple's policies mitigate against this). I have been an Apple developer since 1981 and have stayed with Apple through thick and thin but by God it's getting hard. I don't imagine I will ever switch to Windows but I can foresee a final straw coming at some stage and me going cold turkey and just giving up my dependence on computers altogether. And for those of you innocently wondering why Apple hasn't dealt with this when there are sixteen pages of complaints, check out some of the problems with hundreds of pages of complaints... also unanswered... and dating back years in some cases.

This is a legitimate issue. ****, I even registered on these boards just so I could point out how messed up this is.

I just dropped $650 on an LG Plasma TV with 3 HDMI ports, one of which I was hoping to use on my Macbook 11' intel duo-core from 2007. I've already used 2 different mini-DVI to HDMI types of connections, one is a straight cable that connects from the Macbook DVI to the tv's HDMI and the other is a Rocketfish adapter. The TV will detect that a computer is connected but my laptop WILL NOT DETECT ANY DISPLAYS! That is with the cable. With the Rocketfish it just wont work.

And my sister's Macbook, which only came out a few years ago, worked ONE TIME with the cable and now it is doing the same thing my Macbook did. It'll flash a blue screen when I plug in the cable from the TV but that's it.

I mean come on Apple, dont you make enough millions to pay one of your tech geeks to come up with some sort of patch for this? 😠

This one really help on Mountain Lion. Many thanks.

I was already frustrated, checked with coworker-s laptop and it worked, tried several reboots, shutdow with open lid/start with close lid...

For those of you running Snow Leopard, hold the option/alt key to make "Detect DIsplays" button appear on a settings window

Hi everyone,

I have a macbook pro 13 early 2011 with Mountain Lion installed (I've bought the upgrade from Lion hoping that it could solve the issue). I have the same problem, when I plug my external monitor in mini display adapter to DVI, it flashes a blue screen in the mac and nothing happens after. It fails to recognize the external display. I've tried several suggestions (reseting pram, smc, using different monitors, different cables, etc) but nothing worked so far. I'm now considering installing Win 7 through bootcamp to check if it works..

This is big a headache for me because I just can't work on a 13" screen for more than 30 minutes. I might buy a new computer because of this.

Thanks

Same problem here with a macbook pro early 2011 after install mountain lion with mini display adapter to HDMI

I picked up a rocketfish vga adaptor and now all is well!!!!!

hdmi seems to be out of the question, but the vga picked up instantly! got mine at best buy !!!!