There's a debug log message in Embedded.java with a typo in it: "INITIAL_CONTEXT_FACTORY alread set " Attached is a patch against the 6_0_29 tag, but the issue exists in tc6.0.x/trunk
Fixed in 7.0.x for 7.0.9 onwards. Proposed for 6.0.x
Thanks for the report. Fixed in 6..x and will be in 6.0.33 onwards.