i guess you are on a oracle 9.2 database. In the past i had a simmilar problem and i think i solved it by setting the memory parameters in the dbca manually.
Do not ask why, just try plaing around with the memory settings. Downsize or upsize it. Try manuel or percentage settings.
dbca does a lot under the surface. After copying the files dbca tries to start the instance. I think something goes wrong at this moment, based on your memory settings. The TNS error is just a followup error and not the real reason.
In the long run just try to build a database manually from the command line. If errors occure you would have a better possibsility to trace the problems.
I know I have succesfully created databases using the wizard in the past.
What is the command line for creating databases?
...and the $64,000 dollar question: Why don't any of my Oracle reference books list anything under "Databases, Creating". That would seem pretty basic to me. Aren't there ANY good manuals for Oracle available?
If it's not practically useful, then it's practically useless.