I recently (4 months ago) built a new system to replace my older on. It was 5 years old and I felt it was time to go with a new system. I always do my own builds so I have only what I want and/or need and not a lot of extra crap on the machine.
One thing I did notice though. When installing my software, I only installed the latest ver of Splat. Now when I open up one of my projects, it tells me that I have a reference of a Sonitus delay plugin that it can not find. Although I do have the Sonitus plugins...I can add a new instance of the plugin. I usually just let the plugins install to the default location for that reason, so I'm sure it's not a plug location issue.
Now that I think about it....could it be that the plug it's looking for is a DX plug that did not get installed with the latest ver of Splat? My older machine has had Sonar updated from Sonar X1 if I'm not mistaken. I recall having problems with the Sonitus plugs if I tried to use the VST versions....I had to use the DX version or they would squeal VERY bad. It was like a horrible feedback...I usually experienced it with the Sonitus reverb, but got to where I would just use the DX version of all of the Sonitus FX. It seemed to work fine when doing this.
It's not a critical issue, as I still have the old machine in tact. I can always just open up the project in the old machine and write down the settings of the delay plug and install a new instance of the plug in the project in the new machine. But it's more of a curiosity thing as to why it's not finding the plug when it should be there.