the following steps reproduce this problem.  in summary, when adding two files whose names differ only by a dash and underscore, e.g. a-1.txt and a_1.txt, only the file with the dash in its name will be added, even though fossil add reports that both were added.  this test was conducted using powershell on windows 7 64 bit.  i can test it on windows xp later this week.  i don't have a non-windows box to test this on.

<pre>
PS fossil new test.fossil
project-id:
server-id:
admin-user: rev (initial password is "4cabdf")
PS md test
PS cd test
PS fossil open ..\test.fossil
PS echo "hello" > a_1.txt
PS echo "goodbye" > a-1.txt
PS ls

    Directory:

Mode                LastWriteTime     Length Name
----                -------------     ------ ----
-a---         6:23 PM         20 a-1.txt
-a---         6:22 PM         16 a_1.txt
-a---         6:22 PM       7168 _FOSSIL_

PS fossil add *.txt
ADDED  a-1.txt
ADDED  a_1.txt
PS fossil extras
a_1.txt
PS fossil ls
a-1.txt
PS fossil commit -m "underscore omitted"
New_Version:
PS fossil extras
a_1.txt
PS fossil ls
a-1.txt
PS
</pre>