The honeymoon for European bond rates appears to be over for the Continent's most-troubled economies. After more than a year of interest rates across the Continent moving lower in lockstep—regardless of the country—the last 24 hours show a breakdown in the relationship.

Investors are still pouring into German bunds, much as they are still moving into U.S. Treasurys. But they are selling Italian, Spanish, Portuguese and especially Greek debt.