See the google group topic: "Agent enhancer weird problem"
At this stage this looks like a JRE issue but need to reproduce and investigate.
I am having this issue using Ebean with Play 2.0 Beta. I would be happy to help debug the problem with some guidance.
I am running on 64-bit Linux with OpenJDK 6 update 22.
Apologies, it turns out to be a Play specific issue.
Will close this as unresolved for now.
Can reopen if it appears again.