Frank, This is something that I haven't run across on any honda. Hopefully it's still under warranty. I'm not sure of the cause for this on your CRV, but tightening valves seem a little strange to me because they would normally loosen up a bit over time. An overtightened exhaust rocker can easily cause this to happen but I would imagine this was a problem that originated at the MFG where the valve was overtorqued during assembly rather than the valvetrain tightening up over time. Also, a cracked head/gasket could have caused this to happen(burnt valve) I checked my computer at work for any TSB's(technical service bulletins) or Recalls and found a lot of TSB's but none of them mention this type of problem. If you need any help e-mail me.

Frank
  I have been told a bad timing belt can cause these problems. I have never owned a Honda but I have worked in three of their plants and know the guys and that is what I can recall from memory.