Disklavier

I have had a Mark IV for a few years and really do not use it as much as I'd like.  I kids and wife play but I just listen.  I have a problem when I have not played any of the music on it for a while.  When I decide to play some music all looks normal but it never plays.  I usally have to shut it down, unplug it, then restart it.  I did that over the weekend and it still did not play. Any suggestions? 

I am at an older version of the OS, I think V2.  I need to get to V4 but have been reluctant to do so since it has been somewhat unstable.

As a side note I have noticed references to VirtualPRC.  Is that the same as DKVBrowser?  

Thank you. Merry Christmas

Don Coleman