You may or may not have heard. 6.5 million passwords were leaked from LinkedIn (http://www.informationweek.com/aroundtheweb/security/8-million-leaked-passwords-connected-to/2b7468432b63664e4a6b4f61794763707051756b42413d3d?itc=SBX_iwk_fture_sociative_Security_security). Allegedly at least. It’s possible then that yours is one of them.
If you are using LinkedIn and you are concerned, as well you should be, you can find out if your password is compromised from this (appropriately named) website www.leakedin.org.