[rushmere]

I'm very new to Macs - bought my first Mac (an Intel 20" iMac) about 2 weeks ago. Mac OS is fantastic - why didn't I switch sooner?

It went great for the first 2 weeks, and I've suddenly started to experience a weird display problem.

When I restart, the display comes on correctly, but after a few seconds, it goes into what I can only describe as a psychedelic effect. It looks like it's trying to display using only primary colours, and any text is faint and hard to read.

Here's the really weird bit. If I then connect my second (non-Apple) display, it all goes back to normal again.

If I start up the iMac with the second display connected, it goes psychedelic until I unplug the second display!

So basically, plugging in or unplugging the second display makes the display go back to normal.

Have I messed up a setting somewhere, or could I have a hardware fault?

Any ideas would be very gratefully received.

[GladToBeHere]

That sounds like hardware behavior to me, but I don't recall having heard such a thing before.

[FFL]

create a brand new user and reboot, logging directly into that account.

see if the behavior repeats

[rushmere]

Thanks for the replies.

Still get the same problem with a new user. I'm going to get in touch with Apple, I suspect it's a fault with the graphics card.