Tom,

I also remember hearing about final problems  with some of the 746's. 
Perhaps it was with the PRO, but  some e-ham or google searching  may kick 
up something for you.

If all else fails, I would also vote for the reset.  There's a lot going on 
in these modern radios and  things can get out of whack.

You really should have a dummy load .  Are you sure that all is good between 
the rig and antennas?   If you are running a single coax to the tower and 
remote switching between antennas, be sure  coax and switch are good.   If 
running 2  feedlines to the antennas, what is common to both in the shack? 
Check all connections between  rig and any meters, switches, filters, etc. 
To eleminate  everything else from the equation,  connect  a resonant 
antenna direct to the rig and have your xyl  check the rig's meter.

As for the reset,  perhaps swr protection is kicking in for some reason and 
limiting power.  Maybe a reset will fix it.  Kenwood (at least on the 
TS-2000) offers a choice of full or partial reset.   While a full reset 
blows away everything and restores all to factory defaults, a partial will 
keep memory and menu settings intact.  Check your manual and see if Icom 
offers this feature.

73 and Merry Christmas,
Steve KW3A