This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Looking at the documentation for the hibernate3-maven-plugin:hbm2cfgxml goal, I see this:
Invokes the execution of the lifecycle phase generate-resources prior to executing itself.
I think that setting hbm2cfgxml to run at the generate-resources causes a possible infinite loop and perhaps that is what Maven is complaining about.
I see in the docs that the hbm2java goal runs during the generate-sources phase by default. Try removing the phases from the goals that have default phases.
Try using different execution ids, perhaps those are causing a conflict with the default ids.
Also, try running with the -X option. At the start of the output there will be a build plan report that identifies all of the plugin goals that will run and what their settings are, perhaps that might give a clue.