what happened to those plugins???

Try going into your plugin manager and rescanning your plugins.

I have and im also getting in sonar x2 now error loading plugin do you want to enable anyways on stuff like presonius its crazy ive also tried reading the folders where the plugins are located. what im getting is syth rack missing it shows 2 si drums and one si strings and claims they are missing  this is after the x3c update that ive noticed this

ok what I did was hit rescan all plugins and it refound them some how at first  I was seeing the plugins show up in the plugin finder but it was still saying the plugins were missing when I loaded up my project now everything is normal

Sonar may assume the plug-ins are there, but re-scanning tells Sonar where they are.

I have been seeing a similar issue where the custom vst menu/folder does not see the plugins but if you switch to default/sonar standard vst view for plugins they are there. It is strange because in the add fx bin to track they are there but in add to clip they are not.... :(
 
Possible deleting and building a new custom vst plugs menu will help but with hundreds of plugins building a new file takes a while..