IMac :: 24" Screen Weird Hatched Lines On Screen?

First of all I'm new here so just wanted to say 'Hi', its been great to see all the discussions on these forums and they help a lot with buying tips and troubleshooting so thanks.

Problem #1 I purchased a refurb 24" 2.8GHz imac early May and have been using it since then and so far other than the "normal" gradient issue and a brownish tinge around the edges of the screen it has been good.

Lately I've been using Aperture a lot and first started to notice that in some pictures especially ones with quite a bit of highlights like clouds that there are small hatch like patches in all the pics. I know it isn't the pictures but the imac screen itself as you can see it on the desktop as well. It only seems to be centralized in the upper left hand section of the screen and they seem to be lite purple/blue in color. And like I said its only in patches in certain spots on the screen. Don't know if I'm being over anal about this or is this a problem?

Problem #2 I switched to a solid blue background to check the above problem and notice that there is screen burn in of the top and bottom header in the outline of my firefox window on the blue screen. Between switching windows often and applications very frequently and not leaving the computer at all... what the heck? Not normal for imac screens is it? Heat issue causing burn in? Hasn't been an issue with any other LCD I've ever used.

By the way the imac came in a new white box and was wrapped like new in perfect condition but I popped it open without ever starting it once to make a hard drive swap and the thing was definitely a bit dusty inside so in now way was it just used for a couple weeks before being given back to apple.