Common Factor

I don't know what the problem is but in the last 2 yrs I have had some friends just stop talking to me. It's weird but they just stop returning calls, emails and messages. I don't know what I do that warrants this kind of treatment but it happened to me 2yrs ago with 2 friends and now it has happened again with 2 others. Its more shocking now then before because I used to consider these two to be amongst my closest friends and if they wanted to stop interacting with me they should have atleast given me a reason why. I guess it is just something to do with me because I seem to be a common factor in all this. Wish I knew what, coz I would love to correct it before I lose all my friends.

It's not me, its them :)..it does not matter if I am the common factor.