Alex,
Your troubleshooting method is not sound. Just because an issue goes away on reboot does not necessarily mean that there is not an issue with Sonar. Yes, there is some other issue that is contributing to a problem that is observed within Sonar, but it also depends on whether the outside-of-Sonar issue affects anything else or just Sonar - is it for all apps that use the audio driver? Is it for all apps when the system usage of memory gets to a certain point? What other factors are there?
Computer systems are a lot more complex than a simple "if a reboot fixed it, it can't be the software". Same situation applies for hardware. A reboot often corrects issues that are seen when there is a hardware problem or a driver incompatibility, but that doesn't mean that the hardware isn't the problem or that the drive is fine, look elsewhere. All it means is that giving the computer a nap at least temporarily corrected the problem.
No offense, but it seems like you defend Sonar at every turn as if it's perfect. It's not. And it has different problems on different systems, with different hardware and drivers. If, for example, the driver for a video card happens to interfere with Sonar, it doesn't necessarily mean that the driver has the defect if Sonar is the only application where there are problems.