Has anyone experienced the following problem with the ICOM 720A Xcvr, 
and have you found an easy fix (easy = other than sending it back to 
ICOM!):
 
After the IC-720A has been turned on for about 10-15 minutes the
receiver drops about thirty dB in sensitivity, so that the needle
doesn't move and you have to max out the RF AND AF gain to hear
anything.
 
I find that turning the rig off and back on again clears the problem but
only for a few seconds once the machine is warmed up.  I also find that
keying the transmitter in AM clears the problem, again for only a short
time.
 
I'm currently operating (or TRYING to operate) in Great Britain, so I
do a lot more listening than transmitting; its possible I never noticed
the problem before in CONUS because I was more active.
 
Anyone familiar with this?  I'd appreciate knowing a fix other than
mailing back the box, which is difficult at best from over here.
 
73, WA6VCT (Andy)