Weird Blue Lines on iMac

I woke my computer today to find these weird lines on my screen. The computer works fine beside the lines. It seems like only some colours are affected because some parts of my screen are fine but others have the lines. Also when I'm on a page and i scroll down, it turns all blue instead of lines. Here are some screenshots of what they look like. Any ideas of what could be causing it?
Thanks.

http://farm4.static.flickr.com/3163/2556719971_0f763e4367_b.jpg
http://farm4.static.flickr.com/3257/2556719979_77260a9be4_b.jpg
http://farm4.static.flickr.com/3171/2557551856_840b1e2aac_b.jpg

Give these a try.
Resetting your Mac's PRAM and NVRAM

Depending on which iMac you have, reset the PMU/SMU/SMC
Resetting the iMac (Flat Panel) Power Management Unit (PMU)
iMac G5: How to Reset the SMU
Intel-based iMac, Intel-based Mac mini: How to reset the System Management Controller

Try this as well.
The Apple Hardware Test

Thanks for the suggestions, unfortunately I'm still having the same problem. I guess I'm going to have to take it in and prepare to spend some money.

Go into your system preferences and click on the Displays button then the colour tab at the top. And make sure the colour profile selected there is the right one for your mac. And if it still looks strange then you can always click the calibrate button and use the assistant to fix it up.

Why I'm saying this cause I've seen people with similar symptoms to you and their colour calibration of their screens were out. I dunno how they became wrong but it was an easy fix following the above and a little playing around with the settings.

This might not help you at all but it's worth looking into.

Also there should be in the utility folder something called the ColorSync Utility. Run it, and in the first aid section there too a verify and a repair if needed to to fin up some of your profiles.

blue lines.

the exact same thing has happened to my imac and it has been like that for about 6 months now!

Same...

Hi

My iMac G5 suddenly started displaying the same blue lines as depicted in the screenshots at the start of this post - although not as bad. They're only really visible in light areas of the screen - not on the dark desktop pic, for example.

Have tried resetting the PRAM etc but it wouldn't work - I think due to me locking the firmware when I reinstalled the system a while ago? Tried to reset the SMU but didn't seem to help.

Anyone figure out what the cause of this is? Am wondering if it's hardware related....

Vertical columns of white pixels

Are you referring to the vertical columns of white pixels on the screen shot , second one down.

I have a Power Mac query but the problem with mine is a lot worse

Video cards by the sound and look of it. Run a hardware test.