I haven't noticed any problems in the rain with the same exact tires on my MTB/hybrid commuter. Can you describe how you've fallen? Painted lines, metal grates, railroad tracks, leaves, oil spots, etc. are slippery regardless of what tires you are using. I've spun my rear tire getting moving from a stop (and almost fallen) but that's only because I was in the center of the lane where the cars drip oil.