@lus as I said you in the plugin's page comment, this issue has already been solved, so the best advice I can give you is to upgrade your site to the most recent version (6.6.2 right now). You will see it's worth each one of the five minutes the upgrade takes (if no weird issues appear during the process ;) ).

There is also a workaround that might help you to solve this right now, while you take the decision to upgrade your site. Please check this comment: http://forums.b2evolution.net/cant-link-to-twitter-with-plugin#c104186

@ mgsolipa. Great!!!Thanks! I'v solved the problem using the information from de comment: http://forums.b2evolution.net/cant-link-to-twitter-with-plugin#c104186 as you said.
Just one question. I'm not a expert on informatics, so, is it dangerous for me to use the Auto Upgrade??
Best regards

@lus the auto upgrade is a pretty straight forward process for simple sites (no idea how complex is your site). However, I suggest you to read this manual page http://b2evolution.net/man/auto-upgrade to know all the details.

In addition to that, even when one of the steps of the auto upgrade process is to generate a backup, it's a good idea to be familiarized with terms and other things explained in this other page http://b2evolution.net/man/make-a-backup before to proceed with the upgrade.

Please let us know how it goes.

Regards!

Ok Thank's.
I'll give it a try.
Regards