I created the <JRE_HOME>/lib/endorsed directory and copied javax.annotations.jar to it. Restarted the IDE and all is well. It even builds with ant command line.
It's odd that my library configuration has worked for other projects that called lookup(). But I guess those projects must somehow have preceded the rt.jar with the J2EE_server endorsed path (where my javax.annotations.jar originally lives) when constructing the classpath.
Anyhow ...
Thanks for your help.
[Message sent by forum member 'wnorman']
http://forums.java.net/jive/thread.jspa?messageID=484800