tab completion - new bahaviour or mistake on my part?

[Zenaan Harkness <zen@freedbms.net>]

Tab completion appears to be not working right:

I have a file, ~/todo/todo.txt
I have a folder ~/todo/old/
I want to cat the file.
cd
cat to<TAB><TAB> works as expected, expanding the line to
cat todo/ and showing me the file and directory, todo.txt and old/

But the following does not work:
cat ~/to<TAB><TAB>

This expands to:
cat ~/todo/old/

Why is this?

I don't know yet if this is a bug in my config somewhere - although
I'm pretty sure not since I've tested with disabling .profile and
.bashrc.

Has anyone else seen this?

TIA
Zenaan