Charlie,

Run your gas at 8-10 if you're using our metric gauge, 12-14 otherwise, make sure there is no breeze of any kind..

Also, Mark hit the nail on the head. Bump the electrode size. The charts are not always your friend.

The gas is pure argon right? Is the tank a rental tank? The yellow ball sounds like bad gas or your electrode is contaminated.

I know this is a repeat, just want to make sure you weed out the problem.