There is an interesting post here which describes the circumstances under which Cooper received his 'release'. Basically, Rove's lawyer told the press that if Cooper is going to jail it isn't to protect Rove. Since Cooper thought he WAS going to jail to protect Rove, that caused Cooper to contact the lawyer who gave him the OK.
The request for release was initiated by Cooper, not Rove. Thus, the fact that Rove released Cooper does not mean that Miller's source is not also Rove.
From the article you pointed me to:
---"If Matt Cooper is going to jail to protect a source," Mr. Luskin told The Journal, "it's not Karl he's protecting."---
That quote is specific to Cooper. There is no mention of Miller. If Rove was Miller's source, why didn't Luskin mention her in the quote. I still believe that Miller has another source, one that the Times does not want to reveal. Why is the Times stone-walling. Who are they protecting?