Thanks for the responses. I haven't been on an airplane since 2008 ( got fed up with the poor performance of domestic airlines here in the USA), and even on long drives I've always stopped after about two hours. No recent increases in exercise, either miles or intensity, and I've always drank a lot of water, so doctor ruled that out as a factor (as the article Carbonfiberboy linked in his post). And no recent severe injuries/trauma.
Another thing that linked post by the nutritionist missed: There's lots of foods you've got to stay away from - leafy greens (spinach, cabbage, broccoli, letuce) plus some fish and fish oils (the article almost implies they're good for you), and my doctor also mentioned to stay away from multivitamin supplements for now, as some of them can interfere with the anticlotting properties of warfarin.
Being under 50 yo doesn't really mean much, since DVT can stike at any age (as MAchka's occurance shows),. Its just the probability of occurance slowly increases as you get older, and the probabilty really jumps up when you get over 60 years old. (dang, aging sucks!).
