From QRZ.COM:

As of October 2, Citadel Broadcasting, the parent company of ABC Radio
network, has instructed all 10 of its AM affiliates who had already
converted to IBOC, to cease night time use of the digitial modulation
scheme, citing many complaints from listeners. Some complaints came from
listeners OF the IBOC-modulated stations, while others came from listeners
of adjacent channel stations, that were being interferred with due to the
IBOC bandwidth. Citadel Director of Engineering Marty Stabbert, in a memo
to his staff said, ""In response to the lackluster performance, the limited
benefit and various reports of significant interference, Citadel is
suspending nighttime AM HD operations at this time. Please reinstate your
previous procedures for daytime-only HD operation as soon as possible."
Stabbert says he will attempt to work with Ibiquity, the company that
developed the wide-band digital AM modulation scheme to see if there is a
way to overcome the many problems encountered. Daytime IBOC for the ABC
network affiliates is not affected at this time.