I was testing around with the Oracle Enterprise Manager, in the Console i found that the listener can't be configured error-message "Compute dynamic property takes too long". Reason was that the TNS_ADMIN (Windows, TWO_TASK Unix/Linux??)was set so that just one specific TNSNAMES.ORA file in "c:\oracle" could be used.
When configuring the listener the listener.ora file was also placed in "c:\oracle", and EM could not handle the file in another directory than the default home.
Solution was to delete TNS_ADMIN and put the listener file back to the home-directory, you could also recreate thel listener i think.