I've been suffering with a massive blister in the same place every time I run over about 3 miles for a while now. I've tried vaseline and two pairs of socks which definitely helps but doesn't fix the problem completely. I asked at our running store for their advice and it turns out that new socks are the answer! Apparently cotton retains moisture and you shouldn't run in cotton socks. Who knew?! I suppose it makes sense since you don't run in cotton T-shirts. Anyway, I wasn't sure if I believed it so I bought a pair (for about $10) and took them out for a long run. I had no blisters at all! None in over 5 miles! What an awesome discovery - thank you Emily from Fitniche!