Console STDIN text looks funny

Console STDIN text looks funny

I have a VB.NET solution with several Unix-type console executables that
stream text to STDOUT. The first project creates a file on STDOUT that is
fed to STDIN of the next file.
This was all working for days and suddenly I noticed a strange new issue.
The first file, when I look at it in a text editor looks well and good,
just like it always did to me. However, when I Console.In.ReadLine into a
variable, it's clear that the text is screwed up. It looks like the first
line starts with some unprintable block character and that there is a
space between each character.
I expect a line to be read in like this:
THIS IS MY DATA LINE
But I get this:
$T H I S I S M Y D A T A L I N E
The $ represents an unprintable character. I make lots of changes in a
spurt, so I have no idea what would have caused this, but it is causing me
to lose time I don't have.
Any ideas?