Hi..I've not ever heard/read that UCers are prone to blood clots. There is a form of colitis called ischemic colitis..not related to UC, however. Maybe there's a connection to prednisone use?
I found a good site on it, however, that you might find helpful.
http://www.umm.edu/altmed/articles/ginkgo-biloba-000247.htm
I would caution to maybe not take it if one is on high fish oils or vitamin E.
quincy