Since it is completely impossible for a remote with 380kb of usable memory to hold a CCF file that's 1mb or higher (you even mentioned in an email that you once ended up with a 4mb file) and, since the remote itself will not operate with a corrupted CCF, then something is obviously happening to the file during download.

And, as you have tried multiple PCs including a real serial port, I have to assume at this point that the file is being corrupted either by a bad serial cable (unlikely since you got a new one), a bad port on the remote (ie gunk inside or a cold solder joint), or something is messed up in the RS232 curcuitry causing it to spew volumes of corrupted information.

If you no longer care about the configuration on the remote, you could try uploading a file to it and see what happens. However if the upload becomes as corrupted as the downloads currently are, your remote will be rendered useless.

Or, try using a terminal program and connect manually to the remote - just to see if anything seems odd or garbled. Instructions are in the FAQ for how to connect. For example, a normal Pronto boot screen would look something like:

00
02
04
10
12
14
16
18


Booting...
BOOT,400000[00],UDB V3.0 AMD S2 ,08/21/2000,14:03:39,CRC OK
20
PSOS,404000[02],V1.0 ,09/20/2000,17:24:10,CRC OK
30
_SYS,410000[08],UDB V4.6 ,09/20/2000,17:24:47,CRC OK
60
_APP,440000[11],UDB V5.1 ,09/20/2000,17:28:26,CRC OK
40
_CCF,4b1000[18],N/A ,08/19/200
52
70
74
78
80
92
82
84
86
88
90
94
96
98

LZO real-time data compression library (v1.04, Mar 15 1998).
Copyright (C) 1996, 1997, 1998 Markus Franz Xaver Johannes Oberhumer

using embedded fonts
font 0 = Pronto 8
font 1 = pronto10
font 2 = Pronto 12
font 3 = Pronto 14
font 4 = Pronto 16
font 5 = Pronto 18

_CCF,D.Tonks CL v1.5 [08/19/2003 02:07]
!

Otherwise, there's little else I can suggest beyond that it may be time for a new remote...