Again, I would be very surprised if the graphics card drivers were anything to do with audio performance or general program stability. Windows software doesn't really work in such a way that the two subsystems are related in any significant way.
 
But having said that, if people do weird stuff with the graphics, then the chance of it being a culprit is raised. And in a strange quirk of fate, after asking earlier about how the Now line could possibly be rendered differently, I encountered this for myself earlier.
 

 
This is what it looks like when Sonar hangs - a sadly common occurrence for me, possibly due to a bad interaction with my M-Audio drivers - and yet somehow, the Now line is still rendering properly over the top, as if it's coming from an entirely separate process.
 
So, the answer is yes, Sonar is doing something rather peculiar with that line, so I'm not so surprised that people are seeing unusual behaviour (including it disappearing).

In fact, here are the extra windows that Sonar is creating in order to render these as overlays:
 

 
And here's what happens when Sonar hangs, and the Now line ends up rendering over your desktop instead:
 

There have certainly been graphics/Sonar issues in past releases - I myself had issues caused by one set of video drivers many moons past, so I wouldn't rule it out without a test first.
 
IF your computer has on-board graphics, in addition to whatever graphics card you are using, it is simple enough to temporarily disable your graphics card and use a simple VGA connection to your on-board graphics, JUST FOR TESTING PURPOSES.
 
It may well be something else, but then again, without knowing - you won't know.
 
In the amount of time that posting and reading about how it couldn't be related to graphics, you could have easily tested this out.
 
I am in the process of digging back through prior posts to see if there is anything there that might be helpful.  I did find this link, which is for a prior release, but it might be something to try:
 
http://forum.cakewalk.com/FindPost/2682310
 
In the above link, there is a bunch of discussion prior to the post number I got the permalink for, but I just went to the part that has the thing to try.
 
In addition, I will continue to look for past posts and will post here further if I run across anything that looks relevant.
 
Bob Bone
 

I had gone on a search for the AMD Radeon 1540  - didn't find out it was a typo until after I searched, doh! :)
 
So, after finding your corrected name, I did find the latest drivers for it seem to be from April of this year: http://support.amd.com/en-us/download/desktop?os=Windows%208.1%20-%2064#amd-catalyst-packages
 
The above was given by AMD support for Windows 8.1, and I would double-check, but the above seem to be the latest drivers for your video card.
 
I also looked up your motherboard, and see it does not have on-board graphics, but I still think you could temporarily disable the graphics and test with the standard Windows VGA drivers - just to see if it made any difference.  That whole test would take like 5-10 minutes, tops.
 
Bob Bone
 

@Kylotan having the now time line visible after a crash like that simply tells me the now time line is running under a seperate process/thread so when the rest of the app crashes it hangs around as this particular process hasn't crashed. It should terminate gracefully when the rest of the app crashes but it doesn't. That's not related to the OP's issue.

There is a vital clue here so thanks for this.The chances are when the time line is disappearing that process is actually crashing which is not effecting the rest of Sonar which keeps running. In conclusion the OP is getting the exact opposite symptoms. We still don't know the cause though.

Which leads us onto the question as to what is causing this timeline to crash. So far the betting money is something system specific. We are pointing at the graphics drivers right now... (We need it ruled out).

@Bob I think we both posted the link to the same graphics drivers. Ta

CakeAlexS
@Bob I think we both posted the link to the same graphics drivers. Ta

Well, I suppose that's either good, or bad.  :)
 
At least I was able to FIND the right drivers, after searching for the one with the typo in the name, so I got THAT going for me.....
 
Bob Bone
 

If you are running win Vista Win 7 or Win 8 then in most cases the screen updates go directly to the graphics car. This is meant to reduce the amount CPU used simply to keep the screen updates snappy. It is part of the windows OS. In pre Vista 2d graphics went through the CPU. 
 
It may seem as if its unrelated but in fact the graphics sub system is very important for a good solid system running Windows that is up to date. One can impact the other in very strange ways. 

Anderton
 
However, VV prefers to work in a notation-oriented view. Sonar simply isn't designed to do that. So I highly doubt he'll take the time to find out why he continues to have stability issues others don't experience if all he uses Sonar for is project transfers. Of course it would have been helpful if he'd said that upfront so we wouldn't have spent time trying to find out the source of the problem and help him fix it, but that's life on the internet.   I think it's time to move on because due to his previously stated preference to work in notation, I don't think he would use Sonar even if the Now time moving across the screen created a religious experience 
 

 
Not exactly.  I will likely be using Sonar for a long time since all of my live performance files are in Sonar.   I will not be porting them over to Cubase since there are so many of them.  I don't need any more functionality so I'd prefer not to have to upgrade.   The Now Time bug is very frustrating (as is the bug where saving a drum map adds the name of a previous drum map to the save window making it easy overwrite your other maps ... but I digress).  So actually I still need Sonar but  I can't spend time troubleshooting it.   I recently had a hardware issue that was quite difficult to pin down.   I had to troubleshoot that so the time was well spent.   I just would like the Sonar experience to not be frustrating.   A better title might have been:   Will there be another update or will I have to buy the next version to get rid of the disappearing NOW LINE bug?
 
As for the religious experience, some say that all things are holy so why not the Sonar Now Line?
 

 

> but  I can't spend time troubleshooting it.
 
 It might have taken 15 mins max to test the display driver. Instead you continue to post.
 
> As for the religious experience, some say that all things are holy so why not the Sonar Now Line?
 
If you want it fixed or a bug to be located then give us some feedback, and interact with this forum. People have tried to help and you continue to ignore them. Otherwise please stop moaning. The amount of time you have spent posting here was time you could have spent troubleshooting.... sorry to appear rude but you are wasting our time as well as your own, sorry but we really don't care about how busy you are (you are obviously not that busy otherwise you wouldn't be posting here all the time). We just wanted to help you.
 
Good luck to you...