Eclipse doesn't stop in break points in debug mode

Since yesterday I have problem with Eclipse debugger becasue it doesn't stop in the break points. I searched and I've found out this issue was an old problem related to the JDK 1.6.0_14, but I use JDK 1.7.0_55 and it was working good but from yesterday, to make it work, I should clean application and restart the PC and then run it in debugger and if I do any changes in my code then I should clean and restart the pc again, becuase it doesn't work and I don't know what happened. I use windows 8, Eclipse Kepler Service Release 2 and Oracle Weblogic. Thanks for your help

Solution

If you are using Maven, this is often due to the local source being for a different version than you the executable you are trying to debug. For instance:

I develop v1.0.34-SNAPSHOT and commit to our SVN repository.
The CI server automatically compiles this version
I use the CI server to release version 1.0.34
I deploy v1.0.34 to say Weblogic
I try to debug, and Eclipse gets confused - it has source for 1.0.34-SNAPSHOT but the running version is 1.0.34

Another problem I have seen in older Eclipse versions, is that if two projects import different versions of the same library, then the debugger gets confused as to which source it should use. I've not tested this on Kepler or Luna.