Ok, I've got it.
I also agree it is important to always use latest version but I could not adapt the template to the 'integrity' one which is the one I absolutely prefer . So, I have ' downgraded' to the 2.5 miniBB version and installed without problem the "old" template.
Well, you can still have miniBB 3 and your older templates. This is not a problem, it's possible. But you need to have newer files to test. Specially I think you may try to update to the newer version of bb_func_txt.php. It should be compatible with the older version.
Whatever is needed to be upgraded, are core .php files and all add-ons. You can get such version from the the
Compiler. Then use your templates, but verify them comparing to the newer ones. You need to paste all differences manually. Going template-by-template, you will have a newest version, but with your customized templates. You can do it on your own, also referring to the "
Updates History", or hire me for about $50 for that. Further to that, all future upgrades will be much easier.
I've tried to post a message with a lot of French symbols, but it seems it didn't pass at all. However if I simply type "test", such message goes on. There should be some point to upgrade at least some partial stuff like I mentioned above because of that.
But there also may be some problem with your older template. It seems the message we get is contained in $l_emptyPost variable of the language pack. That means some function cuts off the message to have zero length, but I can't say the reason without seeing the codes. Whatever I have to say because of that, - you must have the latest release with all updated functions installed :)