Thanks. I think reached the next step.
Now the message is:
20015 password_too_short: password too short
Password too short!
{"size":0}
bitshares wallet.cpp:1064 bts::wallet::wallet::create
Unable to create wallet 'my_walletname'
{"wallet_name":"my_walletname"}
bitshares wallet.cpp:1077 bts::wallet::wallet::create
{"filename":"c:/BTSXWA~1.JSO","wallet_name":"my_walletname"}
bitshares wallet.cpp:1241 bts::wallet::wallet::create_from_json
{}
bitshares common_api_client.cpp:723 bts::rpc_stubs::common_api_client::wallet_create_from_json
{"command":"wallet_create_from_json"}
bitshares cli.cpp:540 bts::cli::detail::cli_impl::execute_command
As the password I entered the one I used for the first wallet which I now try to import. It has more than 16 digits and it is definitely the one I used earlier.
EDIT: Found the solution here:
http://wiki.bitshares.org/index.php/BitShares_X_Solutions#Importing_a_JSON_export_from_BitShares_XYou have to put the password in "". Now it worked.
Thanks again.