Can't save or send *some* emails, can't use html signature

[ale0550]

Greetings to all.

After a system reboot my roundcube started to show this strange behaviour: it does not send e-mails with a gif signature, nor saves them to the drafts folder.  No error messages, not even with debug_level=4, just it does not send or save.  Same thing happens with some e-mails which I try to reply or forward.   However some others are sent/saved normally.   I could not figure out what exactly differentiates ones from the others, but it seems that if the e-mail has only text without any attributes (font chage, bold etc.) and no attachments, it goes.

I already reviewed every (or so I think) configuration file, but could not find anything that could explain this behaviour.  Any ideas?

Thanks in advance.

Alejandro Osso.

P.S.:  Configuration is roundcubemail-1.1.3-1.1,  dovecot 2.1.17-2.1.2, web server Apache 2.4.6-6.50.1 and php 5.4.20-67.1  on opensuse 13.1.