Curious latency behavior - problem gone after copying project

[twanger]

Project grew in size with many  tracks plus  three VST instruments and I began having latency issues - the typical sound artifacts - popping, scratching etc.

Of course, increasing buffer size ( to 512) eliminated the artifacts, but the delay was intolerable.  And I know my system should work well with 128 buffers. 

I figured my solution might be to just trim the project down.   

Set buffers back down to 128, where they should be, and copied the project folder to a new one, and tried the copy in Sonar -  NO ARTIFACTS !!!!

I go back to the original - major artifacts at 128 buffers.  Back to the copy - none.  

Would love to hear an explanation...

Using Win 7 Pro 64 bit -  Fireface 800 firewire ASIO interface - Hi-performance i7 rig

[David Baay]

What made you suspect that copying the project might have some effect? Is it on a different drive or just a different location on the same drive? If you watch disk and CPU usage in Windows Resource Monitor, does the crackling project show higher usage in either?