Transmission help?

[elav]

I have a '98 Boxster with a manual transmission. I was driving it today and it was working perfectly. I was in 3rd gear and decided to give it some gas and the engine was no longer powering the rear wheels and I hear a slight grinding sound. The engine runs fine but I hear this slight grinding sound when I put it in any gear and try to disengage the clutch - the transmission doesn't seem to be fully engaging.

Can someone suggest how to start debugging this? I feel like the shifter cables are still in place and the shifter and the clutch feel normal. Is there something on the transmission that can become disconnected and prevent it from fully engaging into gear? My guess is the clutch went out but there was no indication that it was on its way out.

Thanks ahead of time! I did a search but didn't come up with anything.