Model Builder Crashing

I'm using ArcGIS desktop 10.1 SP1 and creating a model with Summary Statistics. I am summing two fields by one case field. Whenever I run the model, just running one at a time, it crashes.

My input file is a dbf. I've tried shortening the input and output file names to less than 13 characters, ensuring no spaces in the path names, and saving to a file gdb or just in a regular file folder, but each time I run it, it crashes. Any thoughts?

Thanks.