As soon as I install the latest Scala IDE nightly on top of AJDT and its m2e configurator, my AspectJ project breaks in such a way that it complains about an allegedly missing Jar: "The container 'AspectJ Runtime Library' references non existing library 'file:\C:\Program Files\Eclipse\eclipse-sdk-3.7\plugins\org.aspectj.runtime_1.7.0.20120418141900.jar!\aspectjrt.jar'" even though the Jar is certainly there alright in the file system.
What's more, if I place a bad syntax error in a file inside my AspectJ project, I get a red wiggly line in the source-file editor, but that error is no longer promoted into the package explorer.
So there seems to be a bad interference between Scala IDE and AJDT. Not knowing who is to blame, I will post this to both the "Scala IDE User" group and to the AJDT forum in the hope this problem can be identified in a collaborative effort.
Go into your plugins directory. Do you see a file named org.aspectj.runtime_1.7.0.20120418141900.jar or a folder named org.aspectj.runtime_1.7.0.20120418141900?
You should have a folder, but your error marker shows a jar file.
It looks like your latest install of AJDT was not correct and didn't unzip the AspectJ jar files before installing them.