After going for so long with no luck, BlueIce snagged me one, and then I tried a little trick and managed to get two more.
Granted it doesn't work if you are suffering from chronic lag, but sometimes the time it takes for you to move your mouse over the egg you want is the time it takes for someone else to come along and take it.
I picked the egg I wanted to try for and placed a tiny dot with a marker pen in the centre of it on my screen... then when I hit the cave button I instantly put my cursor in the middle of the dot and as soon as the page refreshed I clicked... not having to move the mouse gave me that vital second I needed and got me two more (plus I was able to get some for other people as well)
Although I used permanent marker/sharpie the dots have come off with a gentle scratch of a finger nail.
May not help other people, but it worked for me