migration from w2k to win7 broke newlines

Our product uses an Atmel AT91R40008 processor.
The w2k environment is:
* Cygwin 1.3
* eCos 1.3.1
* gcc toolchain arm-elf 2.95

The win7 environment is:
* Cygwin 1.7
* eCos 1.3.1
* gcc toolchain arm-elf 4.6.0

Something in the win7 environment broke some, but not all of the 
trailing newline characters we output via RS-232.  I've looked at the 
printf calls.  There's no practical difference between the calls that 
get truncated and the calls that work.
For instance,

1

start.h:

2

#define START_MSG "\nStart\n"

3

4

start.cpp:

5

printf("%s", START_MSG);

6

-or-

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printf("\nStart\n");

both fail to print the trailing newline, while

1

format.h:

2

#define SPINNING_MSG "Spinning Drive"

3

4

main.cpp:

5

printf("%s %s\n", SPINNING_MSG, drive_text);

will print the trailing newline.

I've tried the -ansi flag to no avail.

Any suggestions to try and track this ?bug/feature? down?
The same code in the w2k environment works fine.
Thanks in advance.