Problem with guestbook after upgrade from 1.11.10 to 1.12

[Kaylen]

I have upgraded my cmcms first form 1.11.10 to 1.11.13 as per instructions in update section, updated al the modules from module manager and then updated from 1.11.13 to 1.12.

Now I have the problem that my guestbook is no longer accessible from the backend and the templates that I use the guestbook in cannot be modified anymore.

I have attached images woth pictures

Guestbook version is 1.4_RC2

I found a post that states my problem, but since I am not so technical I do not understand the proposed workarround and I cannot reply to that post anymore, so thats why I created a new one.

Hope someone can help me?
http://forum.cmsmadesimple.org/viewtopi ... =guestbook