dan le
I am surprised CJ did not say it is the driver. 
dan
jb101
Teksonik will be along soon with one of his obsessive rants about people obsessing about specs, if we're not careful..
Two needless and spam like posts.
This is half the problem on this forum, everyone wants to chime in, even if they have nothing constructive to say.
It makes finding and keeping track of answers to problems, a real pain in the backside. This forum could do with a bit of modding to keep this type of crap to the minimum so that it can be used to resolve issues and pass along tips/info.
Coffee house is the place to chat.
To the OP....
Raising your buffers will more than likely help reduce the wait time from clicking start and may also solve the issue with the buzzing/motorboating.
Also make sure you try to stick to using either 32bit or 64bit plugins without mixing them up. This can cause problems with both latency and glitchy audio.
If it is only happening in certain projects, then try copying that project (save as a new name with it's own audio folder) then start stripping away the plugins to see if there is anything that is conflicting.
Make sure Aero is ON, usual route was to disable it but it's been found that the system does cope better and is much smoother with it running.