One possibility is that the version of the VST being loaded is different from the version used in the original song. If Buzz/PVST is trying to set the value of a parameter that isn't there, maybe that could cause a crash. Also, how did you narrow it down to these specific plugins? Is Buzz throwing an error that points to these VSTs specifically?
invisible_sweater wrote:
The plugins are in the folder, but Buzz doesn't like them anymore.
Just to be clear here: which folder? If plugins don't load when you open a song, but you can still specify the path manually, it might just be that the path is not included in the Vst Directory list in PVST Preferences (or you might need to re-scan).