I created an EJB Project, added a session bean and converted it to a Maven project (via right-click, Configure->Convert to Maven Project). Left default values in the Create POM dialog.

These two warnings and errors now manifest:

ERROR:Java compiler level does not match the version of the installed Java project facet.

WARNING:Build path specifies execution environment J2SE-1.5. There are no JREs installed in the workspace that are strictly compatible with this environment.

It appears to try to switch the Java build settings to use 1.5 although it was configured for 1.6.

Before and after screenshots of settings changes attached.

Project builds again after changing the JRE in the Java Build Path/Libraries back to Java SE 6 (MacOS X Default) and the Compiler compliance level to 1.6