Today I've updated my forum from 1.6.13 to 1.6.14 and I noticed that when I go to control panel to manage my plugins. All my plugins are no longer shown and also I cannot install new ones because they're not displayed
how does your inc/plugins directory look like?
Never mind. It was because of this plugin:
RegOnlyBBCode I'll look into the source later and see why this is happening.