I had a similar problem with Weblogic 9.2 on Eclipse Galileo (the budnled one from Oracle)
The problem is the weblogic server does not support JDK6.
First I had to ensure theat JDK5 was the default; Help/Preferences/Java/Installed JREs - I installed the JDK with weblogic and made it the default.
Then for each project that contributed to my EAR (I had a standard Java Project and a Dynamic Web Project as well as the Enterprise Archive Project)
Right Click each project root in the Proect Explorer
Properties / Java Compiler / Compiler Compliance Level - set to JDK1.5
Properties / Project Facets / Java - set to JDK1.5 (5.0)
Worked for me, might help you or anyone else that journeys here.
Regards
Dave