[tex-live] bug in TeX ?

[Elie Roux]

Hello,

It looks like I have found a bug in TeX : here are the files : 
http://norgz.info/bug.zip

The two files gregorio-good.tex and gregorio-bad.tex differ only in one 
\showthe, and yet the result is different...

If it is not a bug can you explain my mistake, and if it is a bug where 
can I report it ?

At the beginning I thought it was only a bug in omega, aleph and luaTeX, 
so I reported it on luatex (http://tracker.luatex.org/view.php?id=26) 
with the help of Arthur Reutenauer, but after removing all luaTeX and 
omega specific parts, it looks like the bug is also in TeX...

Thank you in advance,
-- 
Elie