I am not sure which module causes this problem
(devt module or plugin). 

This happens intermittently when I work on web
modules: I have modified a JSP but no Java
classes, nor the deployment descriptor, and when I
try to execute the web module from the IDE (from
WEB-INF) it restarts the server. 

I can't tell if this is because the server stopped
when it shouldn't, or if it's because the IDE
thinks it should restart it because I usually
don't think to look whether it's running before I
execute anything :) On the basis that I don't
remember seeing a status message to the effect
that the server stopped it is possible that it
stopped already but perhaps the stopping part is
swift. 

This is moderately annoying if you want to
preserve data in the session while you're working
on a JSP for example. 

I don't have a set of steps that reproduce this
reliably. I'll include an attachment of a web
module that I was working on when I saw this.
Perhaps by adding more JSPs you'll be able to see
it also.