Severe Screen Artefacts post Mountain Lion Upgrade

Thanks for your kind comments animist08. I'm running the iMac in Safe Boot mode at the moment and will continue to do so for the next few hours. So far the horrible artefacts are non existent so I'm crossing my fingers that this indicates a software conflict somewhere rather than a hardware issue.

The big question is where? I'm hoping someone somewhere knows something about this and can point m in the right direction?

.

I'm now wondering if this could be due to my installation of Mountain Lion (ML) having not installed properly?

I'm playing around withNumbers trying to use the versioning system for my spreadsheets but I can't get it to work. The help page for numbers says -

"To browse and restore archived versions of your spreadsheet:

Open the spreadsheet for which you want to access older versions, and hold your pointer over the name of the spreadsheet at the top of the Numbers application window.

A triangle appears."

The heck it does! Nothing happens at all when I do this. Also, the dictation aspect doesn't work either. The microphone picture flickers, so the mic is working, but nothing happens in Pages.

I'm going to have to download and re-install ML I reckon.

Hi Paul.

I did all that and I'm pleased to announce that it appears to have worked!! It's only been half an hour or so since the restart so I'm still cautious but I now get that Triangle in Numbers that I mentioned earlier.

The screen artifacts appear to have gone now. But I will remain sceptical about this until I haven't seen them for at least a week. Well - another couple of hours maybe. LOL!

What appears to have happened this time is that the download was one **** of a bit faster than the first time. My ISP recently upgraded me from 20gbits/s to 60gb/s download. The ML downloader showed 1 hour 36 mins to do the jobs but actually took only about 40 mins. The installer took a further 40 mins.

This time, when ML started up, it automatically located and downloaded n a new version of Java (name ended with 2013 or something). I think it was this that has fixed the screen glitches.

The reinstalled version of ML is 10.8.3. It was 10.8.2 before. Okay, so it's a recent update but I wonder why 'Software Update' didn't inform me about this? Just a coincidence that it is released just as I needed it maybe?

Anyway, I'm off now to see if GarageBand works again in all the accounts on my iMac rather than only the administrator account; and to see if edge detection when preview scanning is now available again in Preview and Image Capture when using my HP C7280 A-I-O printer/scanner. Oh, and also to see if Dictation now works. It didn't before.

Bugger! I've just typed this and possibly I needn't have done! Oh well - here goes nothing.....

Thanks for the tips, Paul. Your good health, Sir!

Thanks Paul.

I'm really pleased that, the graphics issue at least, was a software issue (that I anticipated) rather than a motherboard issue (that I dreaded!).

Sadly it seems that I spoke too soon. The screen artifacts are back, just as bad as ever!

Bollocks!

I'm going to have to repost with the same subject title. My apologies for any inconvenience caused.

In case anyone is interested, I have finally found the answer to this problem.

I have a second monitor attached to my iMac that I have been using as an 'extended desktop' using iMac mini-dvi to DVI-D via an adapter. The second monitor (a Philips 190B) died several months ago so I disconnected it with a view to either getting it repaired or replacing it.

I disconnected the connector from the back of the Philips monitor but I didn't disconnect the other end from the back of my iMac. I used Apple Hardware Tester this morning. AHT insists one has to disconnect all external devices. So I did. I have just rebooted with all re-connected excluding the Mini-DVI to DVI-D adapter. The screen artifects are now gone at last.

BTW - AHT reported no problems, despite my internal optical drive needing replacing - but I don't need AHT to tell me that.

Message was edited by: El Deanio

Since my last post (4 April 2013), I was too embarrassed to come back and report that I hadn't solved the problem after all. It came back with a vengeance. Since then I've been spending my time using CleanMyMac to remove unwanted items and such in the hope I stumbled across the solution.

Anyway, I now wish to register my appreciation and thanks to the Apple Engineers in Cupertino (or wherever they may be) for finally making my irritating screen artifacts go away.

Last weekend I was prompted to upgrade to Mac OS 10.8.4. It didn't mention anything about my problem in the spiel that accompanied the notification but nevertheless I pressed on. I'm really glad I did. Since upgrading to 10.8.4 earlier this week, all those spontaneous graphics seem to gone. Well the vast majority of them at least. Every now and then I see a flicker out thecorner of my eye and I think "Oh Nooo!" But it's okay. The screen is still okay.

So - it's a really huge THANK YOU from me to the Apple Engineers for fixing it for me. I'm really chuffed! 😍

A week has passed since my last post. I have indeed noticed a vast improvement. But it is not perfect, the way it was before.

Those glitches are still there - every now and then. I haven't the foggiest idea why. I suspect Apple was sold a pup by whomever it was sold that them the

ATI Radeon HD 2600 Pro 256 MB. Anyone is going to have a hard time trying to convince me otherwise.

Notwithstanding, the problem no where near as bad as it was. So I'm grateful for this.

I have yet to try out Speech recognition and all the other supposed benefits of Mountain Lion - none of which has worked after I upgraded. They might now I hope.

I might try them out soon to see if they work.

If I can be bothered.

Just had the Logic board replaced for £150 (recovered from someone else old iMac).

Problem now gone - except I still get it bad as ever when I'm using Safari. Nothing else - just Safari.

Any clues to why this is? If not, I'll simply change to Chrome or Firefox as my default browser.