When tested latest jboss tools with creating openshift app, it hit error when retrieving Cartridges(EmbeddableCartridges) lists from devenv. But the same configuration worked well with prod and stage env.
Guess this might be caused by some API differences.

Error logs:
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eclipse.buildId=R3_7_1
java.version=1.6.0_24
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=linux, ARCH=x86, WS=gtk, NL=en_US
Command-line arguments: -os linux -ws gtk -arch x86

Error
Thu Feb 16 12:07:37 CST 2012
Could not load application cartridges

java.lang.NullPointerException
at org.jboss.tools.openshift.express.internal.ui.wizard.ApplicationConfigurationWizardPageModel.loadCartridges(ApplicationConfigurationWizardPageModel.java:144)
at org.jboss.tools.openshift.express.internal.ui.wizard.ApplicationConfigurationWizardPage$13.run(ApplicationConfigurationWizardPage.java:680)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

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eclipse.buildId=R3_7_1
java.version=1.6.0_24
java.vendor=Sun Microsystems Inc.
BootLoader constants: OS=linux, ARCH=x86, WS=gtk, NL=en_US
Command-line arguments: -os linux -ws gtk -arch x86

Error
Thu Feb 16 12:07:37 CST 2012
Could not load embeddable cartridges

java.lang.NullPointerException
at org.jboss.tools.openshift.express.internal.ui.wizard.ApplicationConfigurationWizardPageModel.loadEmbeddableCartridges(ApplicationConfigurationWizardPageModel.java:168)
at org.jboss.tools.openshift.express.internal.ui.wizard.ApplicationConfigurationWizardPage$14.run(ApplicationConfigurationWizardPage.java:693)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)