Because of an error in transferring proof corrections, two instances of νl have been incorrectly set as νlow. 1. In § 5.2, paragraph 4 (bottom of p. 602), the second sentence should read (corrected passage underlined): ``Shifts in these frequency-frequency correlations were found in two AMPs by van Straaten et al. (2005) and Linares et al. (2005) in SAX J1808.4-3658 and XTE J1807-294, respectively, in a way that was best explained by the upper and lower kHz QPOs having frequencies (νu, νl) lower than the ones measured in atoll sources by a factor ~1.5.'' 2. In the legend to Figure 9, the last sentence should read (corrected passage underlined): ``In (b) νu and νl of SAX J1808.4-3658 and XTE J1807-294 have been multiplied by the reported shift factors, whereas a factor of 1.5 has been used for IGR J00291+5934.'' The Press sincerely regrets these errors.