On a serious note

I'm pretty sad about my best friend... she's just stopped talking to me, and I don't know why. We've been friends for a couple years, and seen each other through some hard times, but suddenly she just dropped out of my life without so much as an explanation. My emails have been blown off, under the guise of being too busy at the moment. I've given things a couple months to settle down, and still nothing. Have you lost a close friend? I'm fairly used to it, because military life doesn't lend itself to long term friendships very often, but this was a non-military friend, and someone I used to talk to daily. I'm really depressed about it, I miss her. Life goes on, of course, but good friends are hard to find, and it's hard to not feel like I wasn't a good enough friend, or did something wrong that made her discard our friendship. :(