Check your tnsnames.ora and listener.ora files carefully to see if there are any extra white spaces or special characters. If so, fix them and try it out
Many thanks, I think the error is resolved. But am now facing a new problem.
I can now add the database from the tree, but when I try to connect to the same, it just hangs (OR probably does nothing) forever. I doesnt give me any error as such. Did you come accross something of that sort as well ?