[Elecraft] [KRC2] "No KRC2 found" error

[Dave New, N8SBE]

I've looked through the archives, and have not found a similar situation
to mine, so here goes:

1) I can re-download v1.5 firmware to the KRC2 without a hitch.

2) Every time I try to use the config utility, it first tells me 'v1.5'
firmware is loaded, then it tells me that 'No KRC2 found', with the
usual helpful information on setting baud rate, etc.

3) I've tried this will all the following connection hardware:

   a) Radio Shack "long white" USB-serial cable (this one has worked
with everything else I need for serial communication so far, including
K3 serial, LP-Bridge, etc. etc.) on a Windows XP Home laptop.
   b) Dynex DX-UBDB9 USB-serial cable (this uses the Prolific chip set,
and doesn't work, for instance, with my Icom-7000 memory programming
software, hence the reason I bought the Radio Shack cable on a
recommendation from the Icom software author) on a Windows XP Home
laptop.
   c) A real hardware serial port on a Windows XP Pro laptop.

I've tried setting 4800 bps, 8 bits, no parity, 1 stop, no handshaking
in the COM port property panel under the device manager, as well as
disabling the UART TX/RX FIFO.

Nothing seems to help.  I've spent several hours tinkering with this,
and have not been able to figure out why the downloader can talk to the
KRC2, and the config utility can report the firmware version, but then
balks at any further communication (attempted configuration downloads
fail, as well).

I've also tried pulling all the RS-232-related jumpers except W9 and W10
(RxD and TxD) but it didn't seem to make any difference.  Of course, the
D/L switch is set in the proper position.

Any ideas?  I'm at wit's end, and any help would be appreciated.

73,

-- Dave, N8SBE