So I recently started work on a friends silverstripe website, and I didn't know much about it and have been teaching myself how to work and edit the sit over the course of a month. Recently I updated the software to the latest 2.3.4 version hoping it would fix some bugs that had existed in the older one. Instead, it won't allow me to use the gallery and newsletter modules anymore, giving me the attached errors for each. With the gallery module I already spent a few hours trying everything that I could find in the documentation and the forums, and I even reset the db and started with a fresh install of the module, and now everytime I try to select the extension to show images, it will crash, and if I deselect all the extensions, I get a blank template page, but nothing else. yes, I checked the permissions. The newsletter used to work fine, but now I click on it in the admin page and I get the attached error screen.
I would remove all of the modules, rebuld the site, then install the modules fresh. Move all of you module folders off line, any custom PHP, do a build for the site, then begin to add the modules back. It seems to me you are having conflict issues inside the database. By doing a build with no modules, it should clean up the database and allow the modules to work properly.
Actually, you don't need to do any of that. All you need to do is upgrade the newsletter module to the latest 2.3 compatible version from SVN (which is probably trunk). The gallery module however has not been maintained for ages and ages and is probably not compatible with 2.3.4. The Image Gallery module is probably the best alternative to use.
Thanks for that, I got rid of the old Gallery module, and now have a functioning Image Gallery. I am still having trouble with the Newsletter Module as it won't allow me to add members to the Mailiing List, either through the CMS or the subscription page I generated with the newsletter module OR the userform module I installed later. My understanding by now is that the issue is somewhere in the code of the Newsletter module which is making it problematic with adding users in version 2.3.4.
I am running the latest trunk of the newsletter, though I had the same issue with the stable build.
For adding users to a list always first define a newsletter type under the tab 'newsletter' and choose a group you defined before under security. Then choose in the page subscription form the right newsletter for 'Select the newsletters that you want the user subscript to'. But I'm still using 2.3.3.
Probably something important changed? http://open.silverstripe.org/wiki/ChangeLog/2.3.4