[nb36-rc3; seems to be JDS(quicksilver) specific]
Try to follow these steps:
1) create a WM
2) execute it
3) change context property of the WM
4) execute it again

The deployment progress window shows up but it
stocks in deploy command execution. The server
output contains:

Apr 8, 2004 9:24:05 AM
org.apache.catalina.core.StandardHostDeployer install
INFO: Installing web application from URL
file:/space/certif/testing/quickstart/
 
but the network connection for the IDE to the
server is not closed. So the deployment progress
monitor is still opened and is waiting.

In fact the webmodule is properly deployed, but
the j2eeserver code thinks it's not. So when you
close the progress window and try to execute it
again there is an error message saying that there
is already a webmodule deployed under the
specified context (what is actually correct).

The workaround is to refresh the tomcat server
instance webmodules node and undeploy the freshly
deployed one. Then execute the webmodule again.

It seems to me that this problem arises only when
you follow the scenario (currently I have no time
to play with this - could someone try this?)