funny error with ctags and vim

Hi,

I found a funny problem with tags (well, not that funny since it slows
down my productivity).

I work with Python and the tags worked well until I worked with a file
named "tags.py". Now I keep having that error:

E431: Format error in tags file "itws--herve/tags.py"
Before byte 24

When I rename it to "tag.py", the problem disappears. That's where it's
funny.

I first suspected the tags file itself, but it seems to be correctly
generated: http://bpaste.net/show/7305/

Then I tried to trace down the tag code in vim and tried to hack
"src/tag.c". I expected to find some hard-coded "tags" but the best I
could achieve is not preventing from reaching the definition after error
431 occurred:

--- a/src/tag.c Sun May 16 13:56:06 2010 +0200
+++ b/src/tag.c Tue Jun 22 12:00:39 2010 +0200
@@ -2391,7 +2391,7 @@
if (!use_cscope)