sort not sorting right?

[Bertram Franz]

Hi,

I have an issue with sort. A file

A:B
A:F
AC:B

is, in my eyes already sorted correctly. When running it through sort 
(no options), it comes back with

A:B
AC:B
A:F

Somehow it acts as if -d was specified, but it wasn't. I experimented 
with the -t : option, no success.

How can I sort a file without ignoring colons, or tabs, or spaces?

I tried on different machines with
textutils-2.0.14-2 (RHES 2.1)
coreutils-5.2.1-31 (Fedora Core 3)
coreutils-5.2.1-32 (SuSE 9.2)

On an HP-UX machine I get the desired result ...

Thanks,
Bertram