Charles Schwab has stopped investors from buying RVXCF through online trading.  Now you have to call them up and manually place any trades for RVXCF. 

When I asked them to investigate why this policy has been put in place, they came back with "too many investors got wild prices when they traded it online".  It seems people put in market orders instead of limit prices when trading this stocck...got filled with lousy prices and complained.  

I am surprised that you can even short such an illiquid and relatively low priced stock.