[ivansc]

Hi and welcome to the forums.

Sounds like you have something weird going on with your plugin installs or the declared plugin paths in Reaper. Can you give a little more detail as to exactly what plugins are involved in the error & also show your plugin list from the Options/prefs/Plugins/VST window?
In the meantime, have you tried clearing and re-scanning your plugin paths in this same window?
If Reaper cant find a plugin or if the plugin craps out, it automatically marks the plugin off its list of available plugins until ytou fix the problem AND do a full clear/rescan rather than just a plain rescan.

Be worthwhile checking out the free user guide and the excellent free video tutorials at reaper.fm if you havent already done so.