[Elecraft] K2/100 75 meters lost receive

[2Cents]

Hello group,
 
My K2/100 with KAT2 seems to have lost recieve on 75 meters only. It
transmits fine there but upon releasing the mic it sounds like the coax has
been cut.  This is in a mobile installation using a screwdriver antenna with
a swr of less than 1.2:1.  It matters not whether the ATU is in line or
bypassed--receive sensitivity is very low.  If I tune my antenna analyzer to
the same frequency and hold it close to the radio it will pick that up and
display an s-meter reading, so I know it's not stuck in transmit.
 
All other bands work normally.  
 
Where do I start?
 
Many thanks,
 
Chuck Teague
NN7U