[The Weed]

First, have you done all the optimizations? (Look at the "Help Us Help You" link.) If so, post a Sandra report, maybe people will have suggestions.

Run LatencyMon - with all programs closed - for 10 to 15 minutes. Maybe there is something causing the clicks and pops at a lower buffer. There was a Windows update that introduced latency issues. You need the Windows update from July 26 or later to resolve those issues.

If none of the above help, try the Play/Record Fader "trick". In Preferences>Operation UNcheck "Link Record and Play Faders". Then, when the Track is in Record, drop the Fader to the bottom (Infinity) and leave the Fader when out of Record at Zero. Now when you put the Track in Record, no signal will go out from the Track and when you take it out of Record signal will go out.