The problem is the stuff your using is not working with your monitor. The composite to HDMI cable your using IS NOT WORKING because it's still sending the 480i singal thru the HDMI cable, to the monitor -which only accepts progressive scan signals (ie 480P 720P 1080P, but NOT 480i and 1080i)
What you need is a composite or component to HDMI CONVERTER BOX, which converts the interlaced signal from the component or composite cables your using (eg Wii, Xbox, TV, DVD, etc.) to 720P or 1080P for displays only support that format. You can get them (preferibly) thru amazon or whoever sells electronics... Though amazon has more slection and is far cheaper (priced at around $30-60 depending) than Best Buy for that matter.
If your have your Wii equiped with Component cables (the ones that are red,green,blue), you NEED this one.
Component RGB YPbPr w/L - R audio jacks to HDMI converter box:
Or if you got it hooked up with composite cables (which are yellow, w/ red and white audio cables)...
S-Video/RCA Composite w/L - R audio to HDMI Converter Box:
(You may need to get adiditional HDMI cables for them unless you got a whole ton of spares)
To be honest, if you got Component (RGB - red green blue) cables i'd get the one that for component to HDMI because you'll get a MUCH better and sharper picture. I wouldn't get the one for composite to HDMI unless you don't mind a blurry, distorted picture.
Also, being your monitor has only one HDMI port but if anything else that is HDMI (eg, PS3, X box, HDTV box, Bluray/HDMI DVD player, HDMI Computer, etc.) you want to use, but your using yoer only one port for the Wii via component/compostie to HDMI. You could get a HDMI switch box that allows you hook up 2 or 5 things (depending on the model) that are HDMI, but going to only one HDMI port and you could switch the signals whenever something else is on or off. Depending on what one you get, they range from $10-80, but I found one that has 5 ports for $16!
HDMI 5x1 5 Port Switch/Switcher with IR Remote Support 3D:
Hope this helps.