What has happened to my images ? ? ? ?

Hi,
I have been having issues with poor image quality of my pictures on my PC. It's a strange phenomenon as when I edit in LR3 my image looks ok but, when I export to Flickr/POTN or other web pages the degradation is huge. The only way to describe it is major pixilation and the image is blotchy.
Now, the strange thing is if I go on someone else's PC, the image is ok ? ? ? ? ?
I read on another thread about another similar issue and "ICC profile" was mentioned.The poster said they deleted their ICC Profile and it remedied their issues. I wouldn't know where to begin to do this even if it was the correct thing to do. What is the ICC profile, what does it do and how do I delete it ? ? ?
Can anyone please help me as its driving me nuts
Ian

What gamut are you shooting in? Since all web photos are sRGB, are you soft proofing before the export. Is your monitor calibrated?

Hi,
Thanks for taking the time to reply, I just double checked, my camera is set to sRGB, and my colour space settings in LR3 are sRGB too. I'm not quite sure what you mean by soft proofing, isn't that to do with printing ? I haven't printed anything for a while so I can't say for sure what the image will look like compared to the screen image.
Finally, I have only calibrated my monitor using the basic program that is in the laptop but, I haven't always had these problems, for some reason they just started a few months ago, so I must have inadvertently done something............
Ian

Soft proofing is checking for out of gamut colors as you move a file between gamuts. The gamut move can be the result of printing or just exporting to a jpg file.

Right ok, so how do I go about checking for that ? ? ? I'm on my iPad at present, I'll try it out later this afternoon. I have started to read Rene's 'colour' thread, it's a bit deep for me but I'm trying to make sense of it.......

I do soft proofing in Lightroom 4 on my Mac. I am sure LR 4 on Windows offers the same functions.

h14nha wrote in post #15400328
The only way to describe it is major pixilation and the image is blotchy.

Doesn't immediately sound like a color management issue.
Can you post a screenshot?