I did some tests and found the following things:
When I use the stand-alone tbnl server the bad behavior happens .
When using Apache2 mod_lisp2 to comunicate with sbcl everything
works well
What do you think?
I assume its because mod_lisp keeps one connection open to the lisp side therefore the actual socket handling in terms of http requests/replies happens in apache.
I don't use apache/mod_lisp myself, once i finish my project i'll probably deploy it on lighttpd/fastcgi.