modifications disappear from rich text editor to plain text editor or after registration

[solved]
though i had previously & many times :
- ran updates
- ran cron
- truncate all cache tables (phpmyadmin) (could it be watchdog ?)

... i had allways errors yesterday.

today everything is ok !?!?

so ... i apologize !

thanks

[i come back because after thinking the error was mine, it appears it's probably not :

i paste a text in the rich text editor and then a link on an element of this text;
i switch to the plain texte editor : the link has disappeared (and of course, when i come in the rich one too !)

if i register this node, come back in the editor, then i can paste my link, switch from rich to plain to rich and then register : the link stays

(as it is a second wave of test i don't duplicate the one with images but the problem is similar)]