Some access points have a mode called Auto Channel mode where it will move between up to 11 channels. If the access point is using this feature, HMT140 may work properly in Config mode, but could fail or work very marginally in Transmitter mode. If the access point is using Auto Channel mode, make sure HMT140 has "Auto Find" for the channel and the right channels have been selected for "Auto Find" channels.
Some access points will move between 3 channels (typically 1, 6, and 11). HMT140 Utility software will work with these access points with the Channel Auto Find feature, but the channels that are used must match the channels for which HMT140 is configured.