To the OP,I have had the "no audio",no meters,then sometimes" situation many times,and it is always for me,when the soundcard is acting up,and Sonars Audio Engine plays havoc with the project playing properly.

My particular problem[This time]was,as I'm now running a "bus powered" interface-N.I. KA6,having my "under laptop" USB fans running,[to help this poor dell xps run a bit cooler]which it was,was stealing some of the 500ma the interface required,so Sonar,would do almost EXACTLY as you described,as well as going all white,the new soft option to a BSOD,I reckon,anyway luckily the fans have a switch,and not a problem since.[except the internal fan is now often on loudly,whereas before,it hardly switched on].

So I would certainly look to soundcard incompatibilities,as that Tascam is getting on,and is more suited to when it was released,X1 X2,definitely like their soundcards to be shiny or expensive,compared to earlier versions IMO.