strange behavior of ex constructor from string

[Parisse Bernard]

I'm currently testing the latest version of the Z-factorization code and
found some weierd results that I believe show there is a bug in
the ex constructor from a string.
You can reproduce this bug the following way:
compile the latest
ftp://fourier.ujf-grenoble.fr/pub/hp48/giac.tgz
(make install then make factor)
Try
./factor zimmer7
answer is 0
Looking in my code, it seems that the call
    args.push_back(ex(string(ss2),lst(sym)));
line 480 of polygauss.cc
pushes a 0 instead of the correct expression (i.e. what's in the zimmer7
file)
(you can check this by putting a breakpoint in factor.cc, l.27,
p it->dbgprint() prints 0)
The same call works when applied to zimmer1, zimmer2, zimmer3.
Any ideas?

Bye,
Bernard