Misti,
sounds like you have some additional complexity in one of the features that is making for calculation difficulty or an extremely massive feature and something else happening.
I'd suggest running Data Management > Features > Check Geometry on both features and run the companion Repair Geometry tool on them as well.
If either tool shows or does anything that's likely the cause of the hang. You might have some self intersecting loops. Generally these fault just cause the tools to crash or create no output.
Hardolph
