After Effects SDK

Not sure if this is the place to upload - but I haven't find any other place.

I have recently begun learning AE plugin programming and been studying using projects based on the Skeleton project from the SDK.

While I was training - suddenly the references became unavailable (while actually working) and even when I tried to open a new Skeleton project It was still like that.

Not sure if It's a problem with the SDK / Visual Studio itself.

Anyone here expereienced anything similar?