Very quick blog. GWT 1.6 causing JVM crashes.
We were experiencing similar issues, but the issues were difficult to sort out. It appeared Sun 1.5 JVM's did not have this issue, most of the Sun 1.6 JVM's did (but a newer one did not), and the OpenJDK 1.6.0-b09 also had the issue (issues spanning Windows and Linux boxes).
In the end, for our shop, I found the true resolution to the problem to be:
Remove the '-server' option when running the GWT compiler.