Hello Msartori –
I was able to get the issue resolved. Unfortunately the solution wasn’t incredibly clean and it may be different than the issue you are experiencing.
I have multiple sites, and there were (2) different solutions for each.
First site (easier): All I had to do for this site was delete CMS-tree-view. Upgrade the WP database to 4.1.1, and re-install CMS tree view.
Second site (harder): I performed the same steps listed above, but unfortunately expanding my CMS tree view still didn’t work. First I deleted CMS tree view from the plugins page, then I signed into the WP database using MySQL Admin, expanded the wp_options table and deleted all references to cms-tree-page-view (there were 8 total in my instance). After deleting these references I re-installed CMS-tree-page-view and everything worked like a charm.
