If it ever goes up without the remote signal to trigger it, it's likely a short (or software glitch?) on the receiver. However, in my experience, shorts are usually static (ie the volume would go to max every time you turn it on).

Plasmas and LCDs are not effective interference when in standby, but the culprit could be CFL bulbs (you're not the only one that has ghosts, apparently). If you're using a remote repeater system like Xantech, you can get a CFL or Plasma friendly receiver that is immune to this issue (I use a Xantech system and I wouldn't want to do without).

Hope this helps