When researchers began addressing the electrophysiology of conscious error awareness more than a decade ago, the role of the error-related negativity (ERN), alongside the subsequently occurring error positivity (Pe), was an obvious locus of attention given the fact that they are taken as indices of cortical error processing. In contrast to the clear-cut findings that link the amplitude of the Pe to error awareness, the association between the ERN amplitude and error awareness is vastly unclear, with a range of studies reporting significant differences in the ERN amplitude with respect to error awareness, while others observing no modulation of the ERN amplitude. One problem in the studies obtaining null findings is the fact that conclusions are drawn based on small sample sizes, increasing the probability of type II error, especially given the fact that the ERN elicited using various error awareness paradigms tends to be small. The aim of the present study was to therefore address the issue of type II error in order to draw more certain conclusions about the modulation of the ERN amplitude by conscious error awareness. Forty participants performed a manual response inhibition task optimised to examine error awareness. While the early and late Pe amplitudes showed the expected sensitivity to error awareness, the ERN results depicted a more complex picture. The ERN amplitude for unaware errors appeared more negative than that of aware errors, both numerically and on the grand average ERP. The unexpected findings were explained in terms of (a) latency issues in the present data, (b) characteristics of the manual response inhibition task used and the possibility that it elicits variation in neurocognitive processing, and (c), in relation to possible contamination by the contingent negative variation (CNV), an ERP component elicited during response preparation. Suggestions for future research on how to address the issues raised in the present paper are also discussed.