Water in fuel line?

I just came in from cleaning up around 7" of snow on my 1026r with snowblower. A lot of wind blowing snow around. I have a big driveway and paths to clear so I was out blowing snow for over an hour. Just as I was finishing up, I stopped by my shed to fuel her up....she was running about 1/4 tank. I put in 4 gall to just about fill her up. As I was backing her into the garage, my neighbor signaled me that he was having trouble with his snowblower. So I went right over to finish his driveway and after about 5 min of blowing, the RPMs dropped and power diminished. She was running rough. There was a lot of ice on the hood and grill so I said I would go and let her thaw for a couple of hours, thinking maybe the ice was a factor. So I waited 2 hours and went back out and she ran fine but after bout 20 min, the same thing happened. The ice was back on the hood and grill.

most likely some snow got in to the fuel tank while I was filling or somehow the ice was a factor. Any thoughts on what could be wrong and is there a dry gas for diesel I should use?