UNC storage - the path appears to be an invalid path

I would like to duplicate some backups to a UNC storage. Backup exec 15 gives an error;

the path appears to be an invalid path. Logged in as domain administrator at the Backup exec server. Has all rights at the share. Can access it from the Backup Acces server.

Even given the share everybody all rights.

Tried both dns and ip adres. No difference. Other shares within the network the same error.

Any help appreciated,

Kind regards, Michael