This has happened to me on a few occasions now. The moving timeline disappears completely in Track View. It seems to occur after I come out of the PRV after editing midi but not every time. The timeline is still visible when I go back into PVR though.
If I close down the project and reopen and it reappears but that's not really a satisfactory solution.
 
I found some older threads about this before but with no fix.
Any new thoughts/solutions for this issue?

As a first step please update to X3E if you haven't. Could you also please update your display adapter driver to the latest version and then specify here the make/model/display driver version here. I'm also curious to know your audio interface make/model/driver version (might be idea update the driver and firmware for this if necessary).

Finally could you please run windows update several times including optional updates.

Best rule out if this fixes it first.

Many thanks...

CakeAlexS
As a first step please update to X3E if you haven't. 

I'd assumed as I downloaded X3 in August from the Cakewalk website I would be on X3E but I see that this is not the case! As they say, it is a dangerous to assume.
I'll see if X3E makes any difference although as the problem is intermittent I won't know if it's been cured for a while.
Thanks
 

Check for updated graphics drivers. That's solved the problem for many others in the past.

Anderton
Check for updated graphics drivers. That's solved the problem for many others in the past.

thanks, I have updated both the graphics drivers and Sonar so hopefully the problem won't resurface.
I have the latest drivers installed already for my audio interface (steinberg UR22)